In addition to what Vincent said, it's also a big help to make the SUBJECT line meaningful. Things like the following are not useful:
HELP (of course you're asking for help, we all know that)
URGENT (may be for you, but we're all volunteers here
and it doesn't really help you to
try to strong-arm us!)
SILLY QUESTION
3 QUESTIONS (why not just say what the question(s) is/are?)
Instead, make the subject line say what subject area the question is about!