Most of the tips that follow this one detail the things that you can do to prevent confusing the original poster more than he/she was when posting their question.
To sum them all up; be very careful when posting an answer.
Be sure to PostRealCode. Either check your code very carefully or (better) run in in a small test app to insure that it doesn't have bugs. This is especially important when posting examples for Greenhorns (beginners). If you post pseudo-code or incomplete code that is meant to convey a larger point but isn't expected to run, say so.
If you're in a hurry and don't have the time to do these things or find yourself becoming impatient with the original poster, don't post an answer. It is better to let someone else handle a question than to give an answer that confuses the original post or leads them down the wrong road.
If the question is unclear, ask the questioner to clarify without sounding rude. This will help them find out what exactly they are asking, as this sometimes is a big challenge.