Step-Parents and Almost-Step-Parents

I was watching that episode of One on One where Flex's fiancée (aka Breanna's art teacher) tries to amp up her step-mothering skills on Breanna, and can't quite find the right balance between being there for her as a parent-figure, and staying out of the way.

I'm sure a lot of you have dealt with a step-parent who wasn't sure whether they should try to be an enforcer -of-rules, or a "friend", or something in-between.

What kinds of relationships do you guys have with your step-parents? And for those with good ones... was it always good, or did you have to work at it, and how did you work at it?