When our forefathers created the Constitution, they did so with a great eye toward freedom and unfair prosecution of crimes. As such, they laid out some very specific amendments that help you guarantee those rights. But it is up to you to protect them--not up to the cops who are investigating a crime.
Many people are aware of their rights from watching television and movies: You have the right to remain silent, anything you say can and will be used against you. You have the right to an attorney and if you cannot afford one, the court will appoint one for you. That's all well and good if you get charged and get to court. But is that the first time you should be invoking your rights?