If you are really sure you're not guilty--you had nothing to drink, for example, or you had no drugs in your body or in your possession--this article doesn't apply to you. But if you're not sure whether or not you will be convicted in court, then read on.
There are things that only your lawyer can do for you. He can determine whether there are grounds for suppressing evidence against you, for example. Possibly the officer stopped you for no good, legal reason. If so, all his evidence of your alcohol use may be inadmissible in court. That is not something you can do much about yourself, although it is obviously very important.
The first thing you can do for yourself--other than getting a good lawyer--is to enroll in an alcohol or drug rehabilitation program. Why? Because it will show that you recognize that you have a problem and want to do something about it. If this is your first offense, it will very likely help you avoid going to jail (except for the night they arrested you). Even if it is your third offense, it may greatly reduce the bad consequences of what has happened. It may help save your driver's license, too.
Make sure it's a good rehabilitation program, with certified staff members. Your lawyer may advise you about which programs the local courts prefer or trust. The potential benefits come in a number of different situations if an acquittal is unlikely. It will give your lawyer an argument to use with the prosecutor: "My client is working on his problem. There is no need for further punishment."
If the prosecutor doesn't cooperate, your voluntary participation in rehabilitation is likely to influence the judge who sentences you. If considerable time goes by between the start of your rehabilitation and the resolution of your case, which is probable, you will have a track record with the rehabilitation counselors. They may be willing to testify to the success of your rehabilitation and the unlikelihood of your repeating your offense.
This is not defeatism. You want an acquittal or dismissal of the charge if you can get either of them. Those possibilities depend mostly on your lawyer. Think of this as a fall-back position. But it is something you can do to help yourself--so do it.
To learn more about the possible consequences of a DUI, see DUI Laws by State.