Summary of the guidance here (roughly):

Each person has a unique nature that means most given ideas will probably be additive to EA if you've reflected on it for a bit. So have a low bar to ask questions or make a post, using the shortforum format to publish less fleshed out ideas. 

Some specific useful bits:

• The EA Forum is a flat intellectual hierarchy, so feel free to comment wherever you think you can be additive, despite the title of the person you may be commenting to
• If you've engaged deeply with something recently (read a book most people in EA haven't, took a class at university, etc.) it is probably worth it to try to condense what you learned and share it with others