Watch out with beach cruisers the saddle sits very low, resulting in only using your front thighs. You waist a lot of energy going slow a making frog shaped legs. :P Typically you want to be sitting straight-up. elbows at 40/45 degrees to hold the handlebars, and your leg almost fully straight on lowest point of the down stroke. Efficient and most balanced use of leg and stomach muscles. This is of course for the above posted Dutch granny bike. (In my opinion the best, yes even for a man.) Mountain and racebikes are a different story. Not as relaxed looking as a beach cruiser, but you not riding that bike to be relaxed ;) Oh and stay away from the evil temptation of gears.

Dutch don't mess around.