Fanworks: Always include a category and a rating tag, and for completed fic, include a length tag. (No one's going to jump down your throat if you forget, but a mod may add it later.) Add as many other tags as are accurate and would help someone find this type of fanwork (e.g. if you mention kidnapping once in passing, don't add a tag for it, but if it's a major part of your work, please do.)
Rec List Links & Fests: For rec list links, please only use the tag "category: rec list link." For fests, only use the tag "category: fest/challenge/etc."