How To Handle the Cops if They Knock on Your Door

If you follow the previous guidelines, the cops will be less likely to knock on your door. But what should you do if the cops do show up? Let's go through this step-by-step.
Knock, knock. Who's there?
The cops will want to talk to an owner of the house or apartment, so if your name is on the lease, that's you. If you're not an owner, go find a (preferably sober) owner and tell him/her that the cops are here. Meet the cops outside on your porch or in the hallway of your apartment building. Also, bring one or two (preferably sober) friends out there with you to witness everything. Your friends don't need to be a part of your conversation with the cop, but they should be close enough to hear what everyone is saying.
Do I have to let the cops in?
No. The cops can only come in if: They have a search warrant or arrest warrant There is a real emergency going on (e.g., someone is screaming for help inside) You let them in Most of the time, cops get into parties because hosts let them into parties. All the cops have to do is get you to consent to letting them in. So, they might say something like, "We're going to check around inside to make sure everything is OK in there. OK?" If you don't want the cops to come in, then graciously say something like, "No thank you officer. I don't consent to your entering my house/apartment."
Am I required to show my ID?
Technically, you aren't required to show ID unless you're being arrested, ticketed, or you're driving. In fact, the ACLU recently sued the East Lansing police on behalf of a person who was arrested merely for refusing to show a cop his ID. Always ask, "Am I required to show you my ID? What if I don't feel comfortable showing you my ID?" Nevertheless, we advise that you do show your ID if you have it. As you sort through your wallet or purse for your ID, the cops will often peer over your shoulder to see if you have a fake ID in there, too. Don't carry a fake ID, and you won't get in trouble.
What do I say?
You aren't required to say anything or answer the cops' questions. But, you should at least speak to the cops to find out why they have stopped by your party.
What will the cops say?
The cops will ask questions to try to confirm that a crime is going on. So, they might ask something like, "You're serving alcohol to minors in there, aren't you?" If you get a question like this, do not lie to the cops, and don't try to give a long explanation. Instead, when the cops ask you this kind of question, just politely decline to answer. Speak in a conversational manner. Don't be confrontational. Don't be rude. Don't ever get physical with a cop.
What if the cops give me a ticket?
Accept the ticket, and don't make a fuss. There's nothing you can do about it now, so save it for the judge.
What if they come in even if I don't give consent?
The cops have no right to do this. But, if this happens, simply say, in a voice loud enough for witnesses to hear, something like, "With all due respect, officer, I don't consent to your entering my house/apartment." But, do not become belligerent or physically confrontational.

From  http://www.umich.edu