Oh I love this question. So essentially I think the key for me is to use multiple methods?
For example, not just taking from media or personal experience but to try and pull ideas and information from all sources? I like to create the base idea for a character and then stem from there, or like a group of characters and create the group vibe and then the individual characters afterwards.

Titles also help as well as images? Having my gen of a character helps me visualise who they are too. ♥️