I'm a little disappointed by some of the advice I'm reading here. Clipless pedals, whether SPD, SPD-SL, Look or whatever similar alternative, are vastly superior to not using a clipless system or platform pedals. Having clipless pedals and proper cycling shoes with a stiff sole are absolutely key to maximizing the transfer of power from your legs to the pedals, in addition to keeping your feet properly aligned with and attached to the pedals.

Proper pedaling stroke should be smooth throughout the pedaling cycle so that you're applying power to the pedals at virtually all points throughout that cycle. That includes using your hamstrings and glutes on the upstroke of each leg as well as the quadriceps on the downstroke. Without some means of keeping your feet engaged to the pedals then you're just transfering power on the downstroke of each leg, wasting energy, and not engaging muscles which can do some real good towards improving your speed, endurance, and so on. When you're pedaling properly your shoulders should not be rocking back and forth - they should be virtually motionless.

Also, cycling shoes should not be loose or somewhat loose - they should be tighter than your tightest pair of walking shoes. You're not going to be walking in them for any length of time, and they're not going to be holding as much weight as your walking shoes do. If they're flopping or twisting around on your feet while you're cycling then they're too loose and you need a smaller size (within reason since your feet will likely swell somewhat after cycling for a while).

Pulling up on clipless pedals takes a while to get used to, but soon becomes second nature and you don't think about it all the time. You just concentrate on a smooth pedaling stroke and that's part of it.