Another good rule of thumb is to wait at least two weeks after a show takes place before you start asking for it. Please remember that just because you saw someone at a show taping it, you are not entitled to a copy. It is the sole decision of the taper if/when that show ever gets shared.
B&Ps are an easy way to grow your collection.
Read this page for details about this method of trading and collecting.
Aside from that, srb covered most of it. Especially his rule number 1: Never pay or sell a fan recording. (The term "Bootleg" implies some underhandedness whereas the bands that we trade allow/encourage fans to make recordings for personal use.)
Have fun, and be sure to ask questions rather than make assumptions. There are many finicky traders/tapers out there who can be easily offended, ruining your chance of getting a show you covet.
And most tapers take a lot of pride in their recordings - they've invested hundreds or thousands of dollars and countless hours to get that recording out to you and other fans - don't download a show and then come on here (or any other fan forum) and slag it, no matter how much you dislike it.
And lastly, have fun!