If you have been drinking and you are stopped by a police officer, you have the right to remain silent.  

Do not answer any questions (especially “How much have you had to drink?”).  Anything you say WILL be used against you.  If you are asked to perform field sobriety tests, politely refuse.  These tests are voluntary and your refusal to take them cannot be used against you.  If you are asked to take a portable breath test, you should refuse this as well.  This is another voluntary test that you are entitled to decline.  

If you are asked to submit to a breath (or in some cases blood) test, you will lose your license for a year if you refuse, and your refusal can be used against you at trial.  In some cases however, this may be preferable to submitting to the test.  The best advice in this situation is to ask to speak to an attorney (your right) before submitting to the breath test.