What can a knowledgeable attorney do for me immediately after I've been arrested for DWI?

A lot! As a few examples, a knowledgeable attorney can assist an arrested person in being released from jail by arranging for or posting bond. A lawyer's presence with you, either in person or on the telephone, can also deter the police from intentionally violating your rights and by preventing the police from negligent violations of them too. Here, it should be noted that all persons arrested for DWI who have taken the police breath or blood test, and even a few who have not, have a statutory and\or due process constitutional right to a second independent blood test by their doctor if performed within two hours of arrest. Accordingly, a lawyer benefits the arrested person because he has a greater chance of arranging for and coordinating such a blood test than does the person in jail for DWI.

As a final example, a lawyer can offer advice as to whether or not it would be of any benefit to answer questions, perform exercises, or to make a statement explaining and proclaiming your innocence while you are being video/audio recorded by the police.