I often plan things, do whatever preparation is necessary and keep the appropriate toys handy. But I like for it to feel
spontaneous, so I do all that stuff on my own and just suggest, seemingly out of the blue, that now might be a good time! Like Gunsmoke said, once we start, things tend to take on a life of their own. When that happens, I always just go with it.
When we were a lot busier, we actually had to schedule time to have sex. That was MUCH better than not having sex, but less fun than the way things are now.