Remain calm, be polite.
Police won't usually break down the door of your home unless they believe you have a weapon or they think you might be hiding and refusing to answer the door. If a police officer, detective or FBI agent knocks on the door, ask who it is and then (if you are satisfied that it is the police) open the door. You can tell the police your name and you can verify your address. Be polite but do not answer any questions without first consulting with a lawyer.
Ask to see the search warrant.
The police generally may not search your home without a valid search warrant. Ask to see the warrant. Check carefully to make sure that the address is correct and the warrant is signed by a judge. Make sure that the area of the search is specified. (For example, does the warrant state that the police can search your home? Does the warrant state that they can search your home AND your garage? What about your backyard?). Tell the police that you are not agreeing to any search, but that you will not prevent them from doing their job and searching the area(s) specified in the warrant.
Photograph or video tape the search, but remain at a distance.
You do not have a right to get in the way of a police search. If the police believe that you are impeding their work, they might arrest you or ask you to wait outside. But if you are able to photograph or video tape the search process without getting in the way, you should attempt to do so. Photos and videos could be valuable evidence should the matter end up in court.
Help the police, only if they ask and only if you want to avoid damage to property.
Sometimes the police will ask for your assistance in searching a specific area, such as a cabinet or inside a piece of furniture. You are not required to assist them. If you think you can assist without any chance of leading the police to incriminating or suspicious evidence, feel free to do so, if it speeds up the process or avoids unnecessary damage to your property.
Ask for a receipt.
If the police seize evidence from your home, ask for a receipt. The police will typically give you an inventory sheet of the items taken.
Don't threaten the police.
Never make the police believe that you are threatening them with your words or your actions. Do not make any sudden movements and do not make it appear that you are reaching a weapon. Be polite or don't say anything at all.
Call a criminal lawyer.
As soon as you can, call an experienced criminal defense attorney. It is important for you to find out exactly what has happened and what your rights are.