All of my characters are an extension of myself. For better or worse, they [i]are[/i] me, so I have no problem drawing upon their essence, and thinking like them. Of course, some of them are easier to write for because some are direct representations of me, while others are just a small percentage of me. That being said, given I'm inspired enough to write for them and get into their minds and mannerisms and practically anything and everything that makes them who they are. They also are a compilation of tropes and various concepts I think would work for them. Sometimes it falls flat, but sometimes I get an idea that works.

I think music helps a lot as well. As Lady A had pointed out, music is inspiration. Again, for better or for worse, music can literally help define a character when they're their best or break them apart by rendering them to their worst. I may not always find the best theme for my characters right away because I struggle to find that right song for them, but once I do, I end up finding ten more just like it. This ends up with me building a small playlist for them.