If you dont know your rights very well, I highly suggest researching over them. too many times i've watched the show cops and what not and when the police interigate their suspects, the suspects practicaly give themselves up.
the constitution is a good guidline which also applies to your rights when dealing with law enforcement.
IE: if a cop were to randomly come to you on the street and ask for your I.D., technicaly you dont have to show them anything, if you dont want to talk to them or deal with them, you can simply say "am I being detained, or am I free to go?" the second they say no or your not being detained you can legaly walk away and they cant do anything about it.
If you are detained, you dont have to talk to them either, just simply say "I am choosing to remain silent and wish to see my lawyer."
The 4th amendment comes into play when it comes to your car and home. if you are pulled over and think they may want to search your care, IF YOU HAVE ANY CONTRABAND KEEP IT OUT OF SIGHT.
if they ask you to step out of your car, step out but lock the doors right away, if they ask what that was for, just say its out of habit. If they ask to search, just simply say "I do not conscent to any searches." if they search anyway without a warrant after you said you do not conscent, you can have them arrested for breaking and entering.
biggest thing to remember when dealing with law enforcement is the 4th and 5th amendment. Security of your own person, effects, papers etc. and no self incrimination. Police can and will lie to you, but do not be tricked into telling on yourself.