I'm the one of the moderators of askfedora. Of late, I've seen a lot of new questions come in. I've observed that most of these do not make correct use of the forum and therefore am outlining the good practices of using it here:

1. Search before you post: Search the interweb and then askfedora itself before posting your question.
2. If you have more than one question,post them separately: Do not write a post that says "many fedora questions" and ask them all together. You're to ask each question separately.
3. Frame a question: This is most baffling. It's called ASKfedora, yet most of the queries are not in interrogative form. And yes, questions end in question marks.
4. Ask good questions: Here's a great post that tells you how to ask good questions
5. Use the tools: When you want to post information along with your question, please use the tools, such as quoting, code snippet etc. If folks can't read your questions, they cannot answer them.
6. Use correct tags: Make use of existing tags instead of adding new ones. This increases the visibility of your question. Remember that tags are without spaces, so "fedora16" is not the same as "fedora 16". The latter actually breaks up into two separate tabs "fedora" and "16" which is illogical.
7. Go through the `sticky posts`_!
8. Subscribe to questions you ask/answer/comment: A lot of answered questions are not marked so because the original asker hasn't cared to follow up!
9. Reward your helpers: This is most important. Mark answers as correct, vote up a good question, vote down a bad one, comment for queries. This will make it a better, more knowledgeable forum.
10. If you see someone not using the forum correctly, point it out: Comment telling the person what he's doing wrong. I periodically make corrections to posts, but it isn't really enjoyable.

That's all I can think of currently. I'll keep updating this post as I observe new trends. Please spread the word :)

Edit: Added a page on the fedora project wiki with this list