The first thing that you should do is be patient. Do not rush to hire the first lawyer who you talk to or find on the internet or the first lawyer whose name was provided to you.
DO YOUR HOMEWORK
There is a significant amount of information available for the general public about the law especially the law of drunk driving. Get yourself some information about the principles of human biology that are involved in a drunk driving case, the law and the penalties. Make sure that any lawyer with whom you speak is well-versed in the issues. If that lawyer is not well-versed in the issues, rule that lawyer out.