Before and after using a face mask

I want to know

What should I do before using a face mask, and what should I do after using it?

I just apply it after washing my face, but should I apply toner, mist, or essence as a base? After that...

People usually say to remove it after 15 to 20 minutes; is that correct?

What else do I apply after removing it?

Or is it patting with the remaining pack residue?

I feel like there might not be a single right answer, but I'd like to know some great tips from other users.