Mine is mostly feelings and thoughts.
I put most of my feelings into Minami when I write AtsuMina because we both see things the same way, and it's my understanding of how she feels and think about things. When she loves someone, I know she'll give them her heart wholly, and that's quite dangerous. She's the kind that will be serious when need to be, but really she's just weak inside. I'm just the same way she is, so if people think I write Minami spot on, it's because that's also me.
With Atsuko, it's more of a thought than feelings even though there may be tiny hint of feelings in it. Atsuko is a hard character to write if you think about it. She's the kind of case where she can be anything, and her feelings is always hard to actually write out. She is cute and adorable, yet scary and deadly. She's a spoiled person even though there are times where she gives. Atsuko is everything, therefore, I think she's a hard character to write. The only moments where I can feel with Atsuko, is when she's trying to win Minami back and treat Minami the way she needs to be treated, give everything to Minami and be there for her.
I don't really date, so I don't have personal experiences... and I don't think I rant either... Though, I do need inspirations to write, otherwise, I won't be in the mood to write well....