Don't refuse the test
While it is true that the state may have a harder job prosecuting you without a breath test, the consequences of refusal can make the DUI much worse. Most states impose a much longer license suspension for refusing the test, and make it consecutive to any suspension for the DUI. Many states allow the prosecutor to tell the jury that you refused a test. In some states and in federal areas like national parks a refusal is a separate crime that is as serious as a DUI. In other states there is a longer mandatory jail term and higher fine for the DUI if you refuse.
Do not try to fool the machine.
There are lots of urban legends about things that will "beat" a breath test machine. Some people claim a coin in your mouth will beat a breath test. Other people try to fool the machine by blowing and stopping or pretending to blow. The machines have sensors that let the operator know when you are messing with the machine. If you continue to do so you will be marked as a refusal.
Do not hold your breath
Most police officers will tell you to take a very deep breath and then blow into the machine. This is a perfect formula for a higher test. The amount of alcohol in you breath is directly dependent upon the temperature of your breath. If you hold your breath it warms up in you lungs. Instead of taking a deep breath and holding it before blowing, take several deep breaths and let each one completely out. This lowers the temperature of the breath in you lungs and lowers the alcohol content of your breath. Then take a normal breath, do NOT hold it, and immediately blow into the machine.
If you blow as hard as you can you will run out of breath before the machine can get a reading. You will have to take a deep breath to blow again and the result may be higher. Just blow like you are blowing through a straw. Blow steadily.
Blow for about seven seconds
It takes a little over a liter of breath for most machines to get a reading. It takes about six or seven seconds to blow that amount if you are not blowing too hard. Count seven seconds as you blow (one-one thousand, two one-thousand, etc.) Then stop. The cops will tell you to keep blowing or to blow until they tell you to stop. Their goal is to get the highest possible reading which, because of the increased temperature, may be falsely high. Overblowing is one of the most common ways police manipulate test results. Some officers don't even know this causes higher results because they are trained to do it that way.
Blow again if you are told to.
The test machines in most states average the results of two or more tests. To do this they can only use results that are within .02 of each other. this means that in most cases you must blow more than once. If you refuse additional blows you will be marked as a refusal.
The procedures before the test are critical. To insure that the test is not contaminated by mouth or stomach alcohol the police should observe you for 15 or 20 minutes before the test to see that nothing goes in your mouth and you do not burp, gag or otherwise get something in your mouth that will contaminate the test. They should also look in your mouth before the test to see if you have oral jewelery or anything else in your mouth. Pay attention to what they do. Are the police standing with their backs to you and talking? Are they talking on the phone or anything else? is there a video camera visible in the room? Your attorney will want to know these things.
There is nothing you can say that will help your case, and lots of things you can say that will hurt you. The police are not going to have a sudden change of heart, apologize and un-arrest you. Don't say anything. The only exception is that some states require you to affirmatively state that you will take a test. In those states say "yes" and shut up.
Hire a DUI specialist
DUI cases are very complex. The science alone is beyond most lawyers. You need someone who knows their way around a DUI case, and knows it well. The national College for DUI Defense, Inc. is a good source for skilled DUI defenders. Their site is listed below.