If you are in the U.S. this is absolutely the most important video you can watch. It very clearly details how the system really works, and why it is always bad to talk to the police without a lawyer present.

Note I didn't say, "Never talk to the police." You need someone with you that can understand the law and how work within the system. You never know when they might consider you part of the suspect pool. You can be helpful, just be helpful while protecting your own best interests.