Most important thing is to know exactly what the law says about carrying in your state so you can know precisely what your rights are when stopped by the police, and then don't give them an INCH. It should go something like this:
Officer: Just a minute there.
You: Yes, officer?
Officer: You got a permit for that gun?
You: I don't need a permit, it's open carry (that is true most places, but check local law). Am I being detained right now, officer?
If the officer says "no," say "okay, have a nice day!" and walk! If you're not being detained, you have every right to leave, and there is no reason to stand there any longer than you have to. That only opens doors for your rights to be violated.
If he says "yes," ask him for his RAS - that stands for Reasonable Articulable Suspicion. They have to have a reason for stopping you. They must suspect that you have either committed a crime or are about to do so, in which case, if they can tell you why, you do need to give them your ID, but if they don't have a reasonable suspicion that you may have committed or are about to commit a crime with they can articulate to you coherently, you don't need to do a damn thing. If they give you some BS after the RAS question, just tell them it's not RAS that you've committed or are about to commit a crime and repeat your question about being detained.
This is what I've learned in my travels here, but I have not open carried before (soon, hopefully), so the specifics of this should be left up to those who have gone through it. However, you can find YouTube videos of cop encounters (which are pretty addicting to watch actually) with OCers. The bottom line is, don't give them one single inch unless the laws says you have to.