Everyone of us has started in crypto and if you made a mistake that could have been avoided, I’m sure you wish to had this knowledge before. That's why I listed the best-known beginner’s mistakes here, if you have more, you can write them in the comments.
Don’t confuse public keys and private keysThe public key is your normal wallet address. It is necessary to know it, if you want to send coins to other people. Or you have to give the public key to other people if they want to send coins to you.
In opposite, the private key is like a password that gives you access to your funds on the address. If a stranger has your private keys he can access your wallet and steal your coins.
So please never confuse the two, the public key is always much shorter than the private key.
This could be a public key: 1b5fGK8uhK287FfZN8dk2s41x8nnu8H
This could be a private key: 4sKH4d12d5TfF45BNgf64LgdUTdES5d4HgDJdfHCr55NfKgGDkfH9D6d2hs
Never share your private keys with anyoneAs a result of the point above, this is also important. The private keys are the only access to your coins. If you give away your private key that works like a password, the person who knows your public key and private key has access to your coins and can transfer them to another wallet. So, share never your private key! Also not to friends and other people if they turn out as untrusted.
Don't fall for scams. There are lots of platforms offering 1% profit per day or more. However, these platforms are all scams, as such high profits cannot be earned. In most cases it’s a so-called Ponzi, collecting money from new investors to pay old ones but finally there is no real product and the website will be shut down quickly and the owners take your money. The most famous Ponzi was Bitconnect, crashed in January 2018.
Therefore, if someone promises you high profits, it is very likely that it is a scam, so be careful and only invest money if you are definitely sure that it is not a scam and you know how profits are made. Don’t trust empty promises without proof.
Don't get phished If you log in into a website (exchange, wallet or Bitcointalk) make sure that you are not on a phishing site. A phishing site is a very close copy of the original website, but from scammers and if you enter your username and password, the scammers have them and will steal your coins or accounts, because they have now access. So, make sure you are not on a phishing Website by checking the URL on the top before your login.
The only one you can trust is yourselfThis is maybe the most important point in crypto space. If you follow this and are always skeptical, if you spent your money, you can avoid losses due to scammers. There are lots of scammers offering shady deals to scam Newbies.
And if someone offers you to do a great deal, be carefully. Never send first. A serious partner will send you first or doing this deal via escrow.
Do your own researchIf you want to invest your money in coins, especially unknown Altcoins or ICOs it’s important to do your own research. Don’t trust YouTube videos or article / blog posts from third parties. In most cases this content is paid or from bounty participants. Never base your investment only on this content, it’s required to check the original information about the company by doing a detailed analysis about the project.
Use first hand information, read website and whitepaper and ask yourself if the solution offered by this ICO would be necessary or is it another copy of existing projects. The market for ICOs and existing Altcoins is very hard now and you need a good idea to exist. In addition, you can ask questions in the Telegram or via mail if you have concerns. An honest team will answer you.
Only use content posted by third parties as additional information but not for an investment recommendation.
And please be carefully by looking at ICO-rating-platforms. It's no secret some are involved in a shady business getting better ratings for projects if they pay rating platforms.
Don't invest more you can afford to loseIf you have done your own research and decided to invest in something, it could be wise to have your own risk management. Think about the worst case, it’s every time possible a project fails or cryptocurrency market enters a bear market.
There are stories about people who took a loan and invested in cryptocurrency when Bitcoin was around $15.000. They have now a big loss and problems to pay back the loan. Sad to see his loss:
https://www.newsbtc.com/2018/08/15/cryptohomie-who-spent-almost-150000-on-altcoins-sees-85-loss/So, don’t invest money you need for everyday life if you speculate in crypto and don't take loans.
Don't click suspicious linksMany scammers will try to get your coins or personal informations, so keep this in mind if you click a suspicious link. There are many ways where they will try to scam you. Be very careful when you receive unasked PMs on Bitcointalk, in most cases there are suspicious links, don't click them if you are not 100% sure that they are legit. Better report these messages to moderators, the sender will receive an ban if it was a phishing PM.
Useful comments added from the discussion below: Use escrow if you trade on this forum https://bitcointalk.org/index.php?topic=4907130.msg44205656#msg44205656If you trade on this forum make sure to use an escrow to avoid being scammed. By doing an escrow the buyer and the seller send their coins to a trustworthy third person of the forum and this person starts sending, when both parties have sent to him.
Here ist a list of trusted members offering escrow services:
https://bitcointalk.org/index.php?topic=2439910.0or
https://bitcointalk.org/index.php?topic=276897.0
Don't fall for fake Bitcoin wallets https://bitcointalk.org/index.php?topic=4907130.msg44211169#msg44211169
Dont't do these mistakes in Bounties https://bitcointalk.org/index.php?topic=4907130.msg44220426#msg44220426
Another great list of Beginner's Mistakes https://bitcointalk.org/index.php?topic=4907130.msg44250774#msg44250774
Don't buy wallets and avoid exchange wallets as much as possible https://bitcointalk.org/index.php?topic=4907130.msg44334086#msg44334086
Make sure to teach someone trustworthy how to access your funds in the case you die https://bitcointalk.org/index.php?topic=4907130.msg48652085#msg48652085
If you have something to add you can leave a comment. Best luck to your coins!