When you write, how do you make sure there is enough chartered development in a story but not too much to overpower the actual fetish part of the story?

Short answer: Practice and experience.

Longer answer: No really, there’s no shortcut here. 

Every story requires a balance between action and development (what Jim Butcher calls “Scenes and Sequels” (I’d recommend his whole series of writing advice actually, you can find it on his old livejournal here–start at the bottom and read your way up.) In fact, he says it more artfully than I will, so go read that. It helped me out a lot when I was getting started writing, and it’s advice I still use on occasion now.