First, a warning. There's lot of mixed reports (even in my 3 transactions so far) with BitInstant. Please checkout the review/support threads in the newbie section as well as on reddit (
http://www.reddit.com/r/BetterBitcoinBureau/comments/1ckked/bitinstant_review_thread/)
Now, using BitInstant and Cash is very simple:
- Select Cash / your location, then where you want to have the final deposit made (e.g. bitcoin address)
- Fill out all the details
- Go to CVS/Walmart/etc and find a MoneyGram location. There's usually counters for that or automated booths. I generally prefer the blue express forms at Walmart. Fill in the details (I don't think your real name/address is required on those forms) and the account details that you'll get when you submit the BitInstant form. ZipZap is the middle man here and they'll email you the payment slip
- Pay cash or using debit card at CVS/Walmart and within few mins you can check out zipzap's website and enter the account number to see if it shows up as paid.
- Pretty much in few mins, you'll have your bitcoins delivered at your address. (double / triple check the wallet address and your email address)
You can checkout the order page from bitinstant to see the latest update... for the cash->BTC it is usually quick. A word of caution on this particular method: You might get few $$ missing in your final BTC. Example, BitInstant tells you that you'll get $300 worth of BTC at the end, factoring in all the fees. When you get the BTC, their total worth is shown in the transaction and it might be say 280 or 290. If that's the case, please report back to the above mentioned channels so their support staff can refund you that missing $$ amount (they usually do this by sending the approp BTC to the address again)
I have done a Cash->BTC once (had $37 missing, and got them to refund that after asking several times), did cash -> BitStamp 2 times. This last time was a crazy 1 hr end-to-end in my BitStamp account :-)
Edit: The conversion rate they use is at the time they process your order... They'll tell you that you'll get XYZ amount. Whatever is the BTC rate at that moment, you'll get that much BTC. You don't really "lock-in" a rate with BitInstant, as far as I know. But the cash->btc or cash->bitstamp approach is usually quick. I like the bitstamp approach because I can manage the trade/orders myself on bitstamp's website. Like today, I was anticipating the price to dip so had a trade order set at 130 and 140...and both got fulfilled (and the price went down to 120s and then back up to 140+ in a span of 1-2 hours)