Being on the force myself I have experienced this numerous times before. Though traffic/road policing is not my primary job, I am qualified to intervean if I see need to.
I normally let a LOT of behavior slip, but +/- once a month I see something that really is not acceptable anymore and in which I intervean.

This doesn't always result in a ticket for the offender. I can honestly say that -for me anyway- the behavior of the offender when he/she is spoken to is the real reason why he/she receives/gets out of a ticket.

Therefor, here goes :

Archeon's top 5 ways of getting out of a ticket :

5) If you are signaled to stop, do so immediately. DON'T keep on driving, making the officer pull you over himself. This is NOT a good way to start a neutral conversation. Justifying your behavior with a "Oh, I didn't notice you were signalling me to stop" WON'T work. We all have the natural reflex whenever we see a cop in the street (especially if we've just done something wrong) to watch their every move. Cops know this too.
(Cop's thoughts at that moment : "Oh, and lying too? What does this guy take me for?")

4) Don't try to justify your own offence with pointing to somebody else's. So never, and I mean NEVER say to the officer something along the line of : "Hey, that guy over there is doing the exact same thing as I did, so why aren't you stopping him?"
(Cop's throughts at that moment : "Cause now I'm a bit busy ticketing your ass, that's why !")

3) Don't try to be a smartass. Saying things like : "Haven't you got anything better to do ?" won't help your case. It still surprises me that so many think it will. About 60-70% of all people that get fined feel the need to say things like that. Of course 100% of those people get the ticket they deserve.
(Cop's throughts at that moment : "I don't know of any place I'd rather be right now than right here writing you this nice big ticket")

2) Don't argue. Not about the way you commited your offense (after all, the cop saw it with his own eyes), and certainly not about the way the officer does his job. Admit to your fault.

And most importantly...

1) BE POLITE ! I can't stress this enough. God knows how many people have already gotten out of a ticket by a simple "yes, Sir".
Most people don't understand this however. They think : "if I'm going to get this ticket, I'm going to give this cop a piece of my mind. At least I'll get some stress relieve for my money's worth then". These (most) people think when they get pulled over they will get that ticket no matter what. Wrong, absolutely wong. It's mostly their behavior at that particular time that will them the ticket, NOT the traffic offence itself.

So the "ideal" conversation between officer and offender would be something like this.
Say you've just ignored to give way, creating a dangerous situation for the people coming from your right.

"Good day Sir. I've notice you've just ignored to give way at that last intersection. How do you explain that ?"
* "I don't really have an explanation for it Sir. I wasn't really paying attention. I was stupid of me and there really is no justification for my action".
"That's right. You know I should give you a ticket" (notice the should. At this point you're halfway home)
* "You're right Sir, I won't argue about it. I'm sorry"

At this point I can guarantee you that you've got a 90% chance to get out of the ticket. In the case of the other 10% the offence was probably just too big to let go unfined or the officer is too dutiful or just a plain a**hole. (I won't argue that there are some like that in every corps. Most of them aren't though)