Check and re-check or you get screwed. Also do your research on everything you want (prices included, don't just take 1 persons word for it. There is a beware of spammers thread here that I suggest you check out.
The good news for you now though is now that you've been burnt once, you know what to look out for later.
Note: I kinda think games like this can be good for the younger players coz this way they have an early introduction to just how shady people can be and learn to be cautious with out any of the rl dangers (unless of course you are doing rmt which is just inviting all sorts of trouble for yourself)