Be smart enough not to leave any evidence if you're going to commit a crime. This means wearing gloves (latex or otherwise). Never speak so your voice cannot be recognized, and cover your face. If things get messy, scrubbing the site with bleach and then ammonia will destroy DNA in blood evidence.
Do not get involved with somebody who will flip on you during interrogation. If neither of you say anything, the cops have nothing. Chances are you'll both walk.
Never invite the police into your home if they come knocking. If they want to ask you a few questions about what happened down the street, or your whereabouts for a particular time, they can talk to you on the front porch, otherwise they need a warrant to enter. DO NOT LET THEM IN if they ask. Regardless of their stated intent, if you allow them access they WILL snoop around. Remember, you have a right to your privacy.
If the police come knocking and want you to "step outside" or ask you to come outside to talk, DO NOT DO IT. They can arrest you without a warrant outside of your home.
Never go down to the station unless the police are arresting you. Before saying ANYTHING pertaining to a crime, invoke your right to an attorney - regardless of your level of involvement.
The cops will do anything to manipulate you. They will play "good cop/bad cop" or act nicey nicey. Whatever their method, DON"T BUY IT! Again, invoke your right to an attorney and let your lawyer handle it. Do not accept soda, water or anything while in the station that your prints/DNA could be lifted from. Do not submit to DNA testing or finger printing without a court order.
Keep in mind that cops rarely have an I.Q. over 120, so you are more than likely WAY smarter than they are. Just remember, invoke your right to an attorney who can protect your rights, be polite, keep your mouth shut and don't give them anything to go on.
