Using a plumb line

In addition to adjusting your saddle height, you can adjust its tilt and forward-and-back position.

This adjustment might have some impact on knee comfort, but more than anything else, it affects the power delivery of your pedal stroke.

The classic rule of thumb is that when the pedal is in its extreme forward position, a plumb line dropped from the point of the bone that protrudes just below your kneecap should go through the ball of your foot, bisecting the spindle of the pedal. Bike shops experienced with making this kind of adjustment actually have plumb lines they use for this purpose. If you decide to do it yourself, have a friend eyeball your knee/foot position as you sit stationary on the bicycle.

Making the adjustment
The saddle is clamped to the seat post by a pair of metal rails that are part of the saddle's frame. Loosen the bolt securing the clamp and slide the saddle to the desired position. Don't remove the nut completely or you might have trouble reinstalling it.

If the saddle won't go far enough forward or back, you might need to change the seat post. Clamp position varies from brand to brand.

Saddle Tilt

Too much forward saddle tilt throws weight uncomfortably onto your hands, while too much backward tilt can cause groin discomfort. It's a trade-off you'll have to make for yourself.

Men should start with the saddle level or tilted slightly upward in front. Women may want to tilt it slightly downward, though a well-designed woman's saddle will reduce the need for doing so.

Making the adjustment
This is usually controlled by the same bolt that controls forward-and-back position. Because it comes under a lot of torque as you shift your weight in the saddle, this joint often uses a notched mechanism to keep it from slipping; you'll have to adjust your saddle by full notches rather than partial steps.

To adjust tilt, you shouldn't need to loosen the nut as much as you did to slide it on the rails. Adjusting the seat forward and back might accidentally disturb your tilt adjustment, but not vice versa — convenient, since tilt is the adjustment you're more likely to tinker with.