Be polite and courteous with police
Don't give any reason to escalate the situation. Don't complain about the stop or arrest or argue with the police. Stay calm; control your emotions. Stay in view of the officers, keep your hands in plain sight, and don't make any quick or jerky movements.
Do NOT resist arrest or touch the officer
Even if you are innocent, do NOT resist arrest. It will only add more charges and make your legal situation more difficult for your lawyer. Do NOT touch or threaten the officer, as the police will add "assault & battery on an officer" charges, which alone carry significant punishments. Do NOT "run" under any circumstances. If you run, innocent or not, the jury can be told you fled the scene.
Do NOT give a voluntary statement
You are NOT required to talk to the police when questioned about a crime. Exercise your rights because you cannot be prosecuted for refusing to give a statement, but you can be prosecuted for giving a false or misleading statement. If you do give a statement, it can be used against you. The Miranda warnings do NOT apply to voluntary statements. If you are not under arrest or otherwise "in custody," then those statements can be used against you even without reading the Miranda warnings ("your rights") to you. Anything you say likely will be tape recorded or videotaped with or without your knowledge. To avoid problems and legal fees later, don't give any voluntary statements. (Likewise, do NOT discuss facts of an alleged crime with anyone else including family members and friends. There is no privilege to protect your statements to these persons, so exercise your right to silence).
Do NOT allow searches or seizures
The Fourth Amendment protects you from unreasonable searches and seizures. Unless an officer presents proper credentials and a search warrant, do NOT allow any search of your body, home, garage, business, computer, car, boat or other dwelling or conveyance or property. ONLY when the police have a valid search warrant signed by a judge is it appropriate to give permission to search. If there is a warrant, ask to read the papers before granting permission so that you know the scope of the warrant. Then ask the officers if you may watch as they search and ask to call your lawyer before the search. You never know whether your spouse, children or perhaps a friend or acquaintance (or even a stranger) may have placed or left contraband or other evidence of crime in or on your property. Although less likely, a "bad" officer could also "plant" evidence; therefore, NEVER allow a search UNLESS the office has a warrant.
Do NOT interfere with or obstruct the police
Do NOT interfere with the officer's investigation or interrupt the officer while he/she is interviewing others or searching. Generally speak only when asked (see above--do not give a voluntary statement) and do not assist in showing items or documents or explaining what happened. Do NOT attempt to obstruct the officers in their duties or to destroy evidence or contraband. Keep to yourself and mind your business. Interfering or obstruction an officer in his official duty is a separate crime.
Do NOT give any samples: Body Fluids, Blood, Fingerprints, Handwriting Samples, Clothing or Shoes, etc.
The Fourth Amendment protects against unreasonable searches and seizures, and the Fifth Amendment protects against self-incrimination. While these samples may possibly be compelled by the court, do NOT give samples (1) without obtaining a lawyer to represent your interest or (2) without a court order. Even with counsel, there are situations when samples simply should NOT be given. Samples given with your permission are admissible in court. Also be careful because forensic sciences are not without fault. There are numerous cases in Massachusetts and throughout the U.S. where innocent people have been wrongfully convicted and even sentenced to life imprisonment or death on flimsy hair or other samples.
Do NOT take a polygraph or lie-detector test
A polygraph is NOT admissible in court. Even if you pass a polygraph, police will not necessarily clear you. Because there are ways to "beat" the test, the police will not rule you out if you are a suspect.