I have been hesitant to post anything like this for a couple reasons. 1. I am not the authority on this subject, but I have been around the block a time or two buying/selling for over 15 years on the internet. 2. Scammers read stuff like this and learn from it. But I have watched a lot of people get scammed here and quite a few are avoidable.
With that, here are some things that you can watch for
If you post a WTB thread, you have to be on your game. These are scam magnets. Scammers search for these specifically and they magically have exactly what you are looking for.
If...
Instructions are in the first post of the above thread.