With both the stokers I've ridden with, we got used to riding with each other pretty quick, there was still some learning to do in riding the tandem, though. Stoker #1 had ridden with several other captains over quite a few miles, so more of the learning was on my end.
Stoker #2 puts her left foot down and leans left, I put my right foot down and lean right, so we had to work out what to do there.
Cadences weren't a big issue. Maybe it's easier for the stoker to ride with a masher than with a spinner.
Stoker #1 had a harder time when I coasted, Stoker #2 can sense that pretty easily.
First time I got on the tandem, it just felt completely wrong- weight's in the wrong place, etc. It took about a thousand miles before that feeling pretty well went away. There's been a couple of times where I rode the tandem 500 miles or more without riding my single bike, then when I finally got back on my single bike, it felt completely wrong. I've heard of a few stokers who got back on their single bikes and forgot to steer, too.