Basic tags:
These are the tags you need for each rec:

Category tag - category: [category of rec - tv/movie/book etc]
Fandom tag - fandom name

Featured fandoms:
If you're reccing for the featured fandom, you also need:

Featured fandom tag - featured fandom

Crossover tag:
If you're reccing a crossover, you need a tag for each fandom (and medium if it's a crossover between a tv show and movie, for example), as well as a tag for the pairing and a tag indicating a crossover rec:

Crossover rec - category: crossover

New tags:
There's a link to the list of the current tags at the top of the page. If you need a tag that hasn't been created yet, please leave a comment on your post indicating the tag(s) your rec requires and one of the maintainers will add it for you.