I am no lawyer, either, have a law degree but have not taken the bar exam. Lawyers who don't practice crim law don't know that much about it anyway.
It depends a lot on the seriousness of the crime. Traffic violations are not really crimes, at least not in the same league as those that send you to jail. You should always give a minimum level of cooperation and politeness. If a cop says that the weather is nice, smile and agree with him, and no you didn't realize why he pulled you over.
Allowing a search is another thing. If you have even a chance of having any illegal material on you, then you must decline permission to search. If they had the right, they wouldn't ask for permission. The Fifth Amendment guarantees you the right to be free from unreasonable search and seizure. On the flip side, one cop who wanted to search my vehicle once screamed in my face at the top of his lungs, "Anyone who ever brings up the Constitution is FVCKING GUILTY!!!" Maybe he was right, but he didn't get his search and had to let me go. Unless you are Ned Flanders, always decline a search. Don't let cops in your house or car, just tell them that you will be happy to cooperate fully after they show you a warrant signed by a judge. They will lie and say that they don't need one, or that they will be back in ten minutes with one so you should just let them in now. If a cop thinks you are up to something, he will lie and tell you anything - and that is not illegal. You can't lie to cops, but they can lie to you.
Also in regard to searches, many police wear a recording device, so that they can get you on tape giving consent to the search. If cops want in your house even after you say no, the magic words to make them go away are "I feel intimidated! You guys are intimidating me!" They will go away immediately. Intimidation is what judges balance against you giving consent for the search. If the search is bad, ie not legal, then everything they find cannot be used against you as evidence.
If you are ever accused of a serious crime, then that is the time to not cooperate at all. There's no reason to talk without your attorney present. TV shows are stupid about that; no one ever asks for a lawyer.
Also, if you are stopped at a concert or public place, more magic words that you should know are "Am I being detained?" If they say no, then you walk off. If they say yes, or they stop you from leaving, then that triggers more of your Constitutional rights to kick in and protect you. If they detain you, then the next question is "Am I under arrest?" If so, then you don't say a word until you get to talk to your attorney. All of this comes from a criminal attorney with years defending concert drug busts, and I went over it with my criminal procedure professor who was a prosecutor for 20 years - he agrees that these are the best things you can say.