There are two ways to lower your score: golf better or cheat. We will focus on ways to cheat
Kicking the Ball (the Foot Wedge)
Most effectively used to improve your lie; this maneuver should be done when nobody is watching you. If other players are watching you swing, just continue to take practice swings until the leave. Kick the ball just enough to have a clear shot, but not so far that others will notice. Doing this from behind a tree or bush instantly saves you a stroke.
The Ball Drop
Sometimes you hit the ball into such a bad spot that you can't even kick yourself to a good lie. When nobody is looking just drop a new ball in a better position. You can also go the riskier route of simply picking up your ball and pretending to swing at it. Start making a big deal about how far you just crushed the ball then race to the green. Walk behind the green and drop your ball a 5-10 feet away. Now not only did you not have to pitch back into the fairway, you also just made a great shot for a birdie chance. If you don't get caught, you can save yourself an easy two strokes on the hole. If your foursome questions your shot, create some elaborate story about the ball hitting a tree and bouncing back to towards the green.
Fairway Tee-Up
Teeing up a ball on the fairway lets you hit the ball farther and use your driver for another shot. You can sneak a tee under your ball if your group is far enough away from you. From a distance nobody will notice the ball is higher, especially if you tee the ball slightly lower than your standard position.