I guess several ways work for different tandem teams. For us, the stoker always stays clipped in at normal stops. I always click out of both pedals and use both legs to keep the bike secure and upright, until we are ready to restart. This answer applies to our brand of tandeming, and we ride only on paved roads with a road tandem. I find that with two-sided MTB pedals such as SPD's or Speedplay Frogs it is very easy to clip in when starting. Single sided pedals would not be as easy in my estimation. When I say "normal" stops above, I would make the exception that when stopping on a steep slope, slick road, sand or other extenuating circumstance, it would be beneficial to have the stoker clip out with at least one foot as well.