In 2001 Eric Raymond wrote the quintessential article on asking questions online, How To Ask Questions the Smart Way. Yesterday I think Jon Skeet wrote the quintessential article on answering them, Answering technical questions helpfully.
For anyone who doesn't know Jon, he's a programmer and an author, and he's currently the top rated user on Stack Overflow, a web site dedicated to asking and answering programming-related questions. In other words, he knows a little bit about this. Both articles are worth a very thorough read.