How can diet pills help my weight loss efforts?

Depends. Diet pills work various ways - by appetite suppression, craving reduction, fullness, boosting metabolism depending on the type of pill.
Helps only a little. Over-the-counter diet pills decrease one's appetite a bit (they are related to stimulants). A person's desire to eat can be much stronger that a diet pill's power to decrease his appetite, so he will likely continue to eat too many calories. Also, diet pills don't increase one's desire to exercise. If something as simple as a diet pill actually worked, we would not have so much obesity in america.