1. Don't tell the cops how much you've had to drink
We've got the right to remain silent and we've got the right not to incriminate ourselves
2. Don't take field sobriety tests
Field sobriety tests are 100% voluntary. This means if you refuse to do field sobriety tests they can't immediately arrest you for DUI
3. Don't take a portable breath test
You don't have to take it. It doesn't help you, it helps them, and they are unreliable to boot. Just say no.
4. The moment you feel uncomfortable ask to speak with a DUI attorney
Once you ask for an attorney when you are under arrest, the police are supposed to stop questioning you and take reasonable steps to get you an attorney.
5. Remain calm and respectful to the police
Try to remain calm and hold your tongue. If you don't your actions will be used against you later.