Jump on your bike and put the heel of the foot on the pedal. At this point, your leg should be lock out.
Then place the front foot on the pedal, and make sure the angle between your shin bone in relation to your thigh bone. This is called ‘Holmes’ method. Holmes theory required quite a lot of research, and states that the optimum angle is 25 to 30 degrees, when you leg is at the bottom of the pedal stroke.
You can use a goniometer to do it. If you don’t have one, it won’t make much of a big hole in your pocket.