According to a post on findlaw, the top 3 mistakes when hiring a dwi lawyer are:

http://blogs.findlaw.com/blotter/2012/03/top-3-mistakes-when-hiring-a-dui-lawyer.html

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  1. Lack of experience. An attorney whose practice focuses on DUI — also called DWI or OVI, among other variations depending on your state — is often your best bet. Experienced DUI attorneys know the best ways to reduce or eliminate jail time, fight for you to retain your driver license, reduce your charge to a lesser offense, and even negotiate a plea bargain.
  2. Lack of knowledge. An attorney who’s unfamiliar with DUI laws may not know how to handle the nuances of a DUI case. These may include how to challenge breath tests, blood tests, and police procedures. Traffic and motor-vehicle laws also come into play in DUI cases. That’s why knowledge about your specific jurisdiction is required: DUI, traffic, and other laws are different in each city, county, and state, and they are subject to change.
  3. Lack of commitment. Lawyers are busy people, and usually handle a heavy caseload. It’s best to hire a lawyer with whom you can connect, and who’s committed to getting you the best possible outcome. If you choose an attorney who’s too busy, your case may be largely handled by paralegals or other support staff, or — in a worst-case scenario — fall by the wayside and not get handled at all."