0. Newbies, NEVER DO BUSINESS WITH OTHER NEWBIES, EVER. There are plenty of veteran members to do business with and ALWAYS use escrow. If you're a newbie and you're doing business with another newbie, there's a 100% chance that you will get scammed (or you're a scammer yourself).
1. New account (usually created within the last 3 months, plus or minus)
2. Low-medium message count with vapid posts of little to no contributory value
3. Use of a seemingly realistic first/last name as their forum account name
4. Signs posts with full name
5. Straight out of Newbie mode right into Lending (requesting a loan of course)
6. Straight out of Newbie mode right into Currency Exchange (PayPal, Liberty Reserve, Western Union)
7. Straight out of Newbie mode and selling gift cards/codes/Steam games of any kind (they'll often be purchased with stolen CC info, leaving you holding the bag later on down the road)
8. Any user blatantly claiming to be female
9. New user trying to sell an Apple iAnything
10. Sob stories asking for handouts
11. Never send to a Bitmerch.com address for escrow!!!
12. Scammers will try to scam you out of amounts as little as BTC.001 or even less. Do not think that just because the requested amount is trivial that it's any more legit than a 1000 BTC loan request.
13. Any user who tries to get you to use escrow through Escrow.com is a scammer, PERIOD.
There. Pretty much in a nutshell how to spot a scammer. There's still some finesse to spotting a scammer, but these rules will separate most of the wheat from the chaff, so to speak. Oh, and I guess there's one more rule:
13. NEVER DO BACKROOM DEALS VIA PM WITH NEW USERS. Make sure all deals are negotiated in the open forum for both public record and peer review.
Examples of posts that fit the scammer pattern:
https://bitcointalk.org/index.php?topic=229987.0 angie (Pending, New acct + Wants to buy 100K XRP and wants to see your address that has the XRP, but when escrow comes up, he logs off and disappears)
https://bitcointalk.org/index.php?topic=227927.0 personABCD (Pending, New acct + Loan req, has a small circle jerk of new users that he's ping-pong'ing fractional loans between)
https://bitcointalk.org/index.php?topic=221204.0 Liberty Payout (Scammer, Numerous references, just do a search on his forum name)
https://bitcointalk.org/index.php?topic=213754.0 Chalie215 (Pending, New acct + Loan req)
https://bitcointalk.org/index.php?topic=214277.0 Waterberry (Pending, New acct + Loan req)
https://bitcointalk.org/index.php?topic=212603.0 badgerman (Pending, New acct + Loan req)
https://bitcointalk.org/index.php?topic=188645.0 CryptoTrader (Scammer, New acct + Currency exchanging where you send first)
https://bitcointalk.org/index.php?topic=188674.0 vivithemage (Pending, Old dormant account newly revived and asking for a loan)
https://bitcointalk.org/index.php?topic=186031.0 kidcudi09 (Pending, New acct + Loan req)
https://bitcointalk.org/index.php?topic=185898.0 ashleysly (Pending, New acct + Loan req + Signs with full name + Implied female)
https://bitcointalk.org/index.php?topic=183309.0 theblazehen (Pending, New acct + Loan req)
https://bitcointalk.org/index.php?topic=181429.0 btc-escrow.co (Pending, New acct + Loan req)
https://bitcointalk.org/index.php?topic=180757.0 barneyss (Pending, New acct + Loan req, Highly implausible story)
https://bitcointalk.org/index.php?topic=180246.0 Slix313 (Pending, New acct + Loan req)
https://bitcointalk.org/index.php?topic=173718.0 ionux (Pending, New acct + Loan req)
https://bitcointalk.org/index.php?topic=171031.0 StealthyDamn (Pending, New acct + Get rich quick scam)
https://bitcointalk.org/index.php?topic=173215.0 brie (Pending, New acct + Loan req)
https://bitcointalk.org/index.php?topic=172793.0 badgetman (Pending, New acct + Loan req for 2 BTC)
https://bitcointalk.org/index.php?topic=119896.msg1793008#msg1793008 Bitzing (New acct + Taking MP and not delivering BTC, More info, Credit goes to BCB)
https://bitcointalk.org/index.php?topic=171613.0 nawazish1 (Pending, New acct + Loan req)
https://bitcointalk.org/index.php?topic=170446.0 zakolivers (Pending, New acct + Wants to buy BTC with PayPal. He uses a seemingly real first/last name as his username, so he's gotta be legit, right?)
https://bitcointalk.org/index.php?topic=169922.0 vitalemontea (Scammer, New acct + Peddling digital goods/WU, More info)
https://bitcointalk.org/index.php?topic=165884.0 Flux79 (Pending, New acct + Gift cards)
https://bitcointalk.org/index.php?topic=168669.0 lucyhiggins (Scammer*, New acct + Wants you to link your bank account to his PayPal account)
https://bitcointalk.org/index.php?topic=167429.0 TreePot (Pending, New acct + Loan req)
https://bitcointalk.org/index.php?topic=166991.0 refta (Pending, New acct + Loan req)
https://bitcointalk.org/index.php?topic=166438.0 OMGBobMarley (Scammer, New acct + Loan req)
https://bitcointalk.org/index.php?topic=166014.0 World Commerce (Pending, New acct + Reloadable CC)
https://bitcointalk.org/index.php?topic=145234.0 RobertClemons (Pending, New acct + Attempting to buy BTC with Paypal acct that doesn't belong to him)
https://bitcointalk.org/index.php?topic=163256.0 GoldenAngel (Pending, New acct + "Investment" req)
https://bitcointalk.org/index.php?topic=164166.0 Xnives99 (Pending, New acct + Loan req)
https://bitcointalk.org/index.php?topic=162204.0 DastanX (Scammer, New acct + Loan req, Claims it was filled but probably won't provide a TxID)
https://bitcointalk.org/index.php?topic=161647.0 c0ikws (Pending, New acct + Loan req)
https://bitcointalk.org/index.php?topic=159934.0 ChickaDee (Scammer, New acct + Loan req, Man-in-the-Middle scam, alt of marketersales, More info, Credit goes to John (John K.))
https://bitcointalk.org/index.php?topic=159764.0 ffernandex (Pending, New acct + Loan req, I think this one was meant to be a joke though)
https://bitcointalk.org/index.php?topic=158639.0 TheDarkBanker (Pending, New acct + Gift cards)
https://bitcointalk.org/index.php?topic=157764.0 instaBoost (Scammer, New acct + Money exchange deals, iPhones for sale, More info)
https://bitcointalk.org/index.php?topic=154761.0 BitPanda (Scammer, New acct + Loan req, Loan filled by another new acct Surpbitcoin)
https://bitcointalk.org/index.php?topic=154010.0 rockso (Scammer, More info, Credit goes to Littleshop)
https://bitcointalk.org/index.php?topic=153203.0 Humanxlemming (Pending, New acct + Loan req)
https://bitcointalk.org/index.php?topic=152965.0 MoneypakBuyer (Scammer, New acct + Loan req, More info)
https://bitcointalk.org/index.php?topic=152461.0 tacoman359 (Pending, New account + Microsoft Points)
https://bitcointalk.org/index.php?topic=152120.0 Darkdata (Pending, New acct + Loan req)
https://bitcointalk.org/index.php?topic=151563.0 bennybong (Pending, New acct + Loan req)
https://bitcointalk.org/index.php?topic=151398.0 whathe12 (Pending, New acct + Loan req)
https://bitcointalk.org/index.php?topic=151195.0 kush1218 (Scammer, New account + Gift cards, alt of firstlady0524, More info, Credit goes to Blazr)
https://bitcointalk.org/index.php?topic=94513.00 xavil (Pending, Possible attempt at a fraudulent private BTC purchase, Credit goes to BCB)
https://bitcointalk.org/index.php?topic=150569.0 paysafecardbitcoin (Pending, New acct + Loan req)
https://bitcointalk.org/index.php?topic=150349.0 Intueri (Scammer, More info, New acct + Loan req, Posting history seems to indicate a gambling habit)
https://bitcointalk.org/index.php?topic=148593.0 UncleBuckRIU (Pending*)
https://bitcointalk.org/index.php?topic=146968.0 flavius (Pending)
https://bitcointalk.org/index.php?topic=146788.0 d3adleavez (Pending*, New acct + Loan req)
https://bitcointalk.org/index.php?topic=146362.0 OrangeVonPurple (Scammer*, Possibly alt of marketersales, tacoman359, and OMGBobMarley. Went straight to selling XBoxLive points.)
https://bitcointalk.org/index.php?topic=145505.0 RHCwebhosting (Pending*, Multiple red-flags on this one. Should be pretty obvious)
https://bitcointalk.org/index.php?topic=145274.0 bluedye (Pending)
https://bitcointalk.org/index.php?topic=147357.0 ironcross360 (Pending)
https://bitcointalk.org/index.php?topic=144992.0 ironcross360 (Pending)
https://bitcointalk.org/index.php?topic=144559.0 hiddenoreo (Pending, New acct + Multiple loan reqs)
https://bitcointalk.org/index.php?topic=144582.0 jspring (Pending, Gift cards)
https://bitcointalk.org/index.php?topic=142104.0 flatlinezor (Pending, Gift cards)
https://bitcointalk.org/index.php?topic=143883.0 tantienstar69 (Pending*)
https://bitcointalk.org/index.php?topic=143415.0 tantienstar69 (Pending*, vouched for by audiation)
https://bitcointalk.org/index.php?topic=142058.0 koelen3 (Pending*)
https://bitcointalk.org/index.php?topic=141424.0 claire (Scammer*, Loan requests (check!), MoneyPak (check!), gift cards (check!))
https://bitcointalk.org/index.php?topic=56835.00 SirChiko (Scammer*)
https://bitcointalk.org/index.php?topic=144012.0 realityfalacy (Pending*, Might be legit but the timing of the loan request is suspicious)
https://bitcointalk.org/index.php?topic=141739.0 realityfalacy (Pending*)
https://bitcointalk.org/index.php?topic=141548.0 lakzo (Pending)
https://bitcointalk.org/index.php?topic=141456.0 uhnonamiss (Pending, more Giftcards for Bitcoins)
https://bitcointalk.org/index.php?topic=140690.0 ridgemont4 (Pending)
https://bitcointalk.org/index.php?topic=140846.0 KJTetc (Pending*)
https://bitcointalk.org/index.php?topic=140933.0 blakbeard (Pending*)
https://bitcointalk.org/index.php?topic=140531.0 raven666 (Pending*)
https://bitcointalk.org/index.php?topic=141039.0 cardinalG (Scammer*, More info)
https://bitcointalk.org/index.php?topic=140049.0 cardinalG (Scammer*, More info)
https://bitcointalk.org/index.php?topic=140095.0 AndrewJ (Scammer*)
https://bitcointalk.org/index.php?topic=139935.0 constitution (Scammer*)
https://bitcointalk.org/index.php?topic=139727.0 itai3856 (Scammer, More info)
https://bitcointalk.org/index.php?topic=139257.0 tono18 (Scammer*)
https://bitcointalk.org/index.php?topic=139398.0 tono18 (Scammer*)
https://bitcointalk.org/index.php?topic=137865.0 thomison360 (Pending)
https://bitcointalk.org/index.php?topic=88315.00 unkn0wn12 (Scammer*, More info)
https://bitcointalk.org/index.php?topic=136346.0 furrycoat (Scammer*)
https://bitcointalk.org/index.php?topic=137633.0 SouthernComfort (Scammer*)
https://bitcointalk.org/index.php?topic=136941.0 JonMcAlpine (Scammer*)
https://bitcointalk.org/index.php?topic=136785.0 chillywilly (Pending*, possible alt of cozz)
https://bitcointalk.org/index.php?topic=130251.0 Ploni (Scammer*)
https://bitcointalk.org/index.php?topic=136282.0 marketersales (Scammer*, Accused of scamming then "found loan elsewhere" but no TXID provided)
https://bitcointalk.org/index.php?topic=136306.0 teodor87 (Pending*)
https://bitcointalk.org/index.php?topic=138807.0 shoopwooper (Pending*)
https://bitcointalk.org/index.php?topic=135612.0 shoopwooper (Pending*, "found loan elsewhere" but no TXID provided)
https://bitcointalk.org/index.php?topic=135459.0 Marker88 (Pending, long-dormant 2011 account recently revived)
https://bitcointalk.org/index.php?topic=138131.0 Jakers (Scammer*)
https://bitcointalk.org/index.php?topic=136749.0 Jakers (Scammer*)
https://bitcointalk.org/index.php?topic=134835.0 Jakers (Scammer*)
https://bitcointalk.org/index.php?topic=131217.0 swc1 (Scammer)
https://bitcointalk.org/index.php?topic=133052.0 leominer (Pending*)
https://bitcointalk.org/index.php?topic=132983.0 AnonCard (Pending)
https://bitcointalk.org/index.php?topic=129567.0 SynOps (Pending)
https://bitcointalk.org/index.php?topic=130459.0 drakedog (Pending)
https://bitcointalk.org/index.php?topic=129557.0 heart_mons (Pending*, User has had one successful loan of 5BTC before, but defaulted on another loan)
https://bitcointalk.org/index.php?topic=134921.0 61197da925c1 (Pending*)
https://bitcointalk.org/index.php?topic=129615.0 61197da925c1 (Pending*)
https://bitcointalk.org/index.php?topic=129508.0 Dakster (Scammer*)
https://bitcointalk.org/index.php?topic=126470.0 Dakster (Scammer*)
https://bitcointalk.org/index.php?topic=133368.0 Roxyoursox (Scammer*)
https://bitcointalk.org/index.php?topic=128437.0 Roxyoursox (Scammer*)
https://bitcointalk.org/index.php?topic=128017.0 andrew12 (Old dormant account suddenly revived and now asking for a loan)
https://bitcointalk.org/index.php?topic=126819.0 pereiaex (Scammer*)
https://bitcointalk.org/index.php?topic=127143.0 quirky53 (Pending*)
https://bitcointalk.org/index.php?topic=123435.0 Crookid (Pending*)
https://bitcointalk.org/index.php?topic=120647.0 Metta28 (Pending*)
https://bitcointalk.org/index.php?topic=122729.0 RantinRave (Pending)
https://bitcointalk.org/index.php?topic=122668.0 Serenity.Sapphire (Scammer*)
https://bitcointalk.org/index.php?topic=121136.0 pat231 (Scammer* though I suspect he's less a scammer and more likely just really bad at managing his money)
https://bitcointalk.org/index.php?topic=119831.0 jackdavis1983 (Pending*)
https://bitcointalk.org/index.php?topic=122082.0 hobo66. (Scammer*)
https://bitcointalk.org/index.php?topic=121998.0 Ssoftware (Pending*)
https://bitcointalk.org/index.php?topic=120233.0 Bitcoinscene (Pending*)
https://bitcointalk.org/index.php?topic=119871.0 ChrisNelson (Pending*)
https://bitcointalk.org/index.php?topic=119384.0 CoinCleaner (Scammer*)
https://bitcointalk.org/index.php?topic=121012.0 LionHeart (Scammer*)
https://bitcointalk.org/index.php?topic=119824.0 LionHeart (Scammer*)
https://bitcointalk.org/index.php?topic=118514.0 Gretchen (Scammer*)
https://bitcointalk.org/index.php?topic=99233.00 noobularkid (Scammer*)
* Account appears to have been abandoned once it was flagged as a scammer, or became apparent he wasn't getting a loan.
Please note that the accounts listed above aren't necessarily or automatically assumed to be scammers. They just fit the description, so to speak.
Examples of posts that fit the pattern that were successful:
https://bitcointalk.org/index.php?topic=141182.0 hardup (Successful Loan!, 2.0 BTC, Several weeks late, but eventually paid back)
https://bitcointalk.org/index.php?topic=158761.0 shibaji (Successful Loan!, Used collateral, 10.0 BTC)
https://bitcointalk.org/index.php?topic=141215.0 Currencevents (Successful Loan! 4.0 BTC, https://btcjam.com/listings/1573)
https://bitcointalk.org/index.php?topic=149335.0 Jenger (Successful Loan! 0.5 BTC)
https://bitcointalk.org/index.php?topic=137766.0 MoneypakTrader.com (Successful Trades!, Has completed a few successful transactions. As always, use caution, even when dealing with senior members)
https://bitcointalk.org/index.php?topic=122658.0 xx78213 (Successful Loan! 0.2 BTC)
https://bitcointalk.org/index.php?topic=134918.0 polymorphous (Successful Trade! 2.0 BTC)
TLDR: Be careful before you freely give away your coins. From the evidence collected here, you stand substantial chance of getting ripped off if lending to someone who fits the scammer profile. If that chance is worth making an extra 1-10% on your money, I can't stop you.