I recently went in for a bike fitting, and was told that I needed to fix my position on the bike. Here are some tips I was given:
First, sit up straight, and with good posture (back flat, chest out, chin down) on your bike (easier if on a trainer). Bend over from your hips, keeping the same good posture. In this position you will be sitting more on your pubic bone (bothersome at first, still trying to get used to it). Also, I've noticed when I'm in this position my thighs tend to bump my tummy. When I have the tummy bump going on, I know I've got it right.
About the feet: if you were standing around tippy-toed, you could only stand that way for a little while before your calves got too tired. But if you stood there flat footed, your calves could stand to be that way all day. Same goes on the bike: less fatigue for your calves if you ride flat-footed.
If you can read this, take a pull.