I generally use these tags:

• title
• artist
• album
• albumartist
• date
• discnumber - only if there are multiple
• genre - I have set genres I use, and I also place the country and sometimes city in here.
• tracknumber

Ones that seem neat that I should use:

• discsubtitle
• language
• artistsort
• albumartistsort - Starting to try thee two 'sort' tags now though.

Maybe notable ones I don't bother with are:

• ?