Relaxing, making sure your stoker isn't trying to steer or control the bike, and very importantly, making sure your stoker remains on a parallel plane with the frame of the bike. When a more experienced captain told my wife this, our balance problems ceased. If there's any leaning to be done, you do it, not her. My wife and I aren't particularly strong or particularly fast (except downhill), but we're a good working team. When I need power from her (usually on a short steep uphill) I let her know and she's right there to do her part. Having said that, there hasn't been a hill that we couldn't eventually get up or a ride we couldn't finish. When Zona says "twogether" he's right in so many ways.