Getting out of a speeding ticket is a bit of an art form; but if you're prone to a lead foot, it's a skill you need to master. You have approximately 20 seconds from the time the cop steps out of the patrol car and strolls to your window to make a judgment call and decide which card to play.
If you can't come up with a good excuse, try to say something funny that will make the officer laugh. Law enforcement is a serious job, so humor is an easy way to throw them off their game. Memorize a few good one-liners for an easy way to get on a cop's good side.
If that doesn't work, or you're just not that funny, try one of the these other methods. Be warned, some of them can be very risky. Oh, and if you get caught lying to an officer, you didn't hear these from me!