(Not) Talking to Cops
Anything you say to the police can be used against you and your friends. Whenever the cops ask you anything besides your name and address, it's safest to say:"I am going to remain silent. I want to see a lawyer." The cops are then legally required to stop questioning you. They probably won't, so just keep repeating it. Say it loud enough for witnesses to hear.Don't wait for the cops to read you your rights. They usually won't. Law enforcement agents are legally allowed to lie, and they're trained to be manipulative. The only thing you should say to them is,"I am going to remain silent. I want to see a lawyer." (Don't sign anything, either, without showing it to a lawyer first.)
Searches
Any time the police try to search you, say:"I do not consent to this search." This may not stop them, but it could get evidence thrown out in court later. This is important, because you might have something on you that is technically illegal (like a pocketknife that's too long), or the police might plant evidence on you. However, don't physically resist when cops try to search you, because you could get hurt and charged with assault.
Any time the cops try to search anything connected to you, say:"I do not consent to this search." Keep saying it, loudly enough for witnesses to hear. This is true for your body, your car, your house, your garage - anything. It's also true if the cops have a search warrant. There might be a technical problem with the warrant that only comes up later.