One of the things police look for in a DUI stop is if you have trouble finding your documents. They will claim this is a sign you are intoxicated. You can avoid this by having your registration and insurance papers up to date and together in the same place - not in the bottom of the glove box - not together with the expired registrations. Have those papers and your license out and ready when the officer comes to the window.
Keep yourself safe
Many people get in a scuffle with police, or in some case even shot, where there was no need for it to happen. Police are on the lookout for their own safety. If you do something they think is a danger to them, they will react with force. When the lights go on, signal and stop promptly at the first safe place. Stay in the car unless told to get out of it. Keep your hands in sight. Do not make sudden moves. Do not argue with the police. Do not resist if they decide to arrest you.
Shut up. I say again SHUT UP.
The famous comedian, Ron White, tells a story about being arrested for public drunkenness, He says "I had the right to remain silent, but I didn't have the ability." You have the right to remain silent - do it. Police will ask you questions: "Do you know why I stopped you?" "Have you been drinking?" "Do you know what time it is?" The purpose of these questions and every other question they ask in every case is to get evidence to use against you. The one thing you should say is "I am going to exercise my right to remain silent." Say it ONCE. Then do it. You can't talk yourself out of a DUI arrest, only into one. There are only two possible exceptions to this rule. Those are spelled out in Steps 6 and 7.
Do not do stupid people tricks
The officer may tell you to get out of the car for sobriety tests. These tests may include an eye test, walking the line, standing on one leg, counting, ABC's, touching your nose or other tests. Most officers do these tests wrong and don't know it. They are not looking for evidence that you are not impaired, they are looking for evidence to arrest you. This means don't give them that evidence. Get out of the car if the police tell you to get out - the police have the right to order you out of the car. The police do not have the right to MAKE you do sobriety tests. Do not do them. Police arrest a large number of sober drivers based on these tests. They will try and make you do them. They will try to talk you into them. Remember Step 3. Shut up and don't do the field tests. Stand there mute.
Do not consent to a search
The police may ask you if you mind if they search your car or your person. Do not consent to a search of your car or your person. It cannot help you. It can only hurt you. Do not argue or struggle if they search you or your car. Remember Step 3. Shut up.
Ask for a lawyer
If the police take you to another place you are under arrest. They do not need to say "you are under arrest." They do not need to handcuff you. They do not need to take you to jail. If you are taken anywhere else or required to submit to a breath, blood or urine test anywhere, you are under arrest.
This is one of the two exceptions to Step 3 (Shut up). Ask for a lawyer and shut up. If they read you your rights - ask for a lawyer and shut up. Do not be surprised if they don't read you your rights. Do not be surprised or upset if they don't actually get a lawyer for you.
Take the breath, blood or urine test.
In every state you must to take a breath, blood or urine test. In many states it is a crime to refuse a test. In every state there is an extra license suspension if you refuse the test. Take the test.
In some states you must verbally agree to take the test. If you are in one of those states, this is the final exception to Step 3 (Shut up). Say yes and shut up.
This doesn't mean you should be a potted palm tree. Pay attention. Watch the officer carefully before a breath test. Remember how long he waited and if he looked in your mouth. Remember what he said and did. If it is a blood test, don't look away when they take your blood. Watch them carefully. Did they swab the place where they stuck you and with what? What color was the rubber stopper on the blood tubes?
Don't try to fool with the breath machine. Take 3-4 deep breaths before the test, Let them all of the way out. Take a normal breath, do not hold, blow for 7 seconds, and stop. Blow again if told to.
Call a lawyer
As soon as you can, call a lawyer who specializes in DUI defense. This is not a case for the guy who did your divorce or a real estate lawyer. DUI's are complex and require a specialist to defend them properly.