I use the "standard" method of determining seatpost height and orientation by pedaling backwards with my heel on the pedal and raising the seat until my knee is straight, then putting the pedals at 3/9 o'clock and determining seat front/back by dropping a "plumb" from the knot below my knee until it bisects the pedal spindle. Works really well for me. Of course, you need to modify for coaster brakes.