If you have a court date coming up, plead not guilty--you can always change your plea later--and ask if you qualify to have a public defender appointed to represent you. If you don't, then get legal advise from a criminal defense attorney in your state. Since this is the first time you have had to deal with a criminal situation, you are-fortunately-in unfamiliar territory and should admit to guilt without knowing all of the ramifications.
A plea of "not guilty" entered at the first court appearance (arraignment) preserves all of your rights and keeps all of your options open. If you plead guilty at arraignment you will lose the opportunity to determine whether there are legal defenses to the charge. Some people think that a "not guilty" plea will be frowned upon by the judge but good judges understand that you have a constitutional right to enter a plea of "not guilty" and to cause the prosecution to actually prove the charge. In Washington State, where I practice DUI defense, I have seen some judges encourage defendants at a DUI arraignment to enter a plea of not guilty. They do so in the interest of fairness and to permit the accused to explore all the options with a good defense attorney.
Mr. Lampert and Mr. Fox are correct. Since this is your first time getting arrested, your attorney will have all the ideas as to what to do and how to do it. So consider www.dui-help.com or similar search for a DUI attorney near you. Enter the Not Guilty Plea.
The short answer: NOT GUILTY. It would be advisable to have an attorney retained to assist you even at these early stages. The first step in the process is pleading Not Guilty at the arraignment, which is where the Judge or a Magistrate will read the charges and the maximum penalties. In many circumstances, your attorney can waive this court appearance and schedule your case for a Pretrial, which is where the attorney and the city or county prosecutor discuss possible resolutions. Even though it is your first time, it is very important, in my opinion, to retain an attorney who is well versed in DUI. This is a complex area of the law, and includes penalties that may stay with you for the rest of your life.
Should you have any further questions, please do not hesitate to contact me.