It's a fine line you have to walk. You be polite to them and if they have you by the balls you tell them semi-truths within reason as long as it's not confessing to something very serious. I mean if he stops you and says "do you realise you were THIS far over the limit?" you might respond with "I'm sorry officer, I didn't realise the limit was X in this area, I suppose I might have been going a little above the limit? I was looking for such and such do you know the way to get there?" or something. Don't flat out admit to having 5 kilos of coke in the boot of the car or had 40 pints of guinness before sitting behind the wheel, nom sayin?
If you have an attitude of "I ain't sayin' shit to you, nigguh" then he is going to make it difficult for you.
First of all, do not tell "semi-truths" to cops - semi-truths are semi-lies and lying to a cop is an offense in and of itself, and quite a serious one at that.
You said that a response to a "do you realize you were THIS far over the limit" might be: "I'm sorry officer, I didn't realise the limit was X in this area,
I suppose I might have been going a little above the limit? I was looking for such and such do you know the way to get there?"Why would you make such an extraordinarirly stupid statement? First of all you're admitting that you don't know the limit in the area and admitting that you were indeed going over the limit. And to add insult to injury you are trying to play "footsie" with him.
If he's pulled you over, he has a reason (or at least a pretense), so why step into shit by talking more? The smart thing to do when you're pulled over is to be calm, polite, and provide your license (or name, address and date of birth) along with your car registration and proof of insurance, and then say nothing else.
Again, the cop isn't there to be your friend, to cut you a break, to tell you you've been a bad boy and give you a slap on the wrist, or to listen to and absolve you of your sins.
I've got off with light stuff like parking tickets but I've also ended up in jail a few times because I was DRUNKKKK and had gone beyond the point of no return!!!!!! But if I'm sober I can talk myself out of most situations because I learnt how to charm people from the best charmers in the WORLD, EVER - THE IRISH!
You've gotten off parking tickets? Oh, well then... let's all listen to your advice! I mean, shit, that's some jedi mind-trick worthy stuff right there.