According to this former attorney, now a professor, you should never talk to the police. Now, I should clarify that this is more to do with being interviewed as a potential suspect or witness. You should always have a lawyer present, and you should remain silent, and express your intention to remain silent, until one is available. Especially if you're innocent.
I should warn you that both videos below are on the lengthy side, the first being 27 1/2 minutes, and the second a little over 21 minutes. However both videos contain information which everyone should have.
More information is available at Flex Your Rights.