Determining what plea you should enter to the court will determine how the rest of the process will go. Your plea will determine how future trials and the rest of the current court case will proceed.
Unless you have a ton of evidence, 800 witnesses, and full video coverage, plead guilty. Why? Well, for one, the judge will always believe the cop over you. The officer is licensed in the state where the ticket was given, the equipment was probably checked before and after the stop, and the officer is certified to operate the equipment. Even if the officer saw your vehicle traveling in excess of the speed limit, they can say that, in their proffesional experience, they can visually determine the speed of a vehicle. This is probably true and the judge will admit this as evidence that you were traveling in excess of the speed limit.
Some states may have a "No Contest" plea. This plea means that you are not saying that you are guilty, just that you are not contesting the charges. In most cases, this is what to plead when you want PBJ.
Ok, you have a line of witnesses out the door, you had your speedometer inspected that morning and after the stop, it just so happens your car was on CNN from a helicopter and everything says you are not guilty. Then, and only then, plead not guilty. Judges hate getting up and going to work like the rest of us and can't wait to go to lunch or go home for the day. They like things to move along smooth and quickly. Some courts even hold the trials until the end of the docket.
When you plead not guilty, you have the chance to ask the officer questions about the stop and a chance to give your testimony. In most cases, people end up incriminating themselves and the judge will give them a stricker fine than others that have gone before you. I've heard the following too many times, "Your honor, there is no way I could have been going 65 in a 55, my cruise control was set on 62!" You have just told the judge that you were exceeding the speed limit and the judge will probably give you the full points and full fine. Never, never, say you were traveling in excess of the speed limit. The only semi-safe answer is to say that you are not sure how fast your were going, but this should only be under a guilty plea.