Don't refuse the test
While it is true that the state may have a harder job prosecuting you without a blood test, the consequences of refusal can make the DUI much worse. Most states impose a much longer license suspension for refusing the test, and make it consecutive to any suspension for the DUI. Many states allow the prosecutor to tell the jury that you refused a test. In some states and in federal areas like national parks a refusal is a separate crime that is as serious as a DUI. In some states there is a longer mandatory jail term and higher fine for the DUI if you refuse.
Do not struggle
In some states police take the blood sample right by the side of the road. In all cases a blood test involves sticking a sharp needle into your vein. If you struggle you will only get hurt.
Most people want to look away when their blood is drawn. Don't. Pay attention to the person drawing your blood, the procedures and materials used. Who drew the blood? Was it a nurse, police officer or the janitor? Did the person have a name tag? What was done before the test? Was your arm swabbed before they stuck you? How was it swabbed - in circles or wiped across? What was used to swab your arm; was it an alcohol swab or something else? Was there a stain like iodine on your arm after the swab? What did the blood draw tubes look like? What color were the stoppers on the ends of the tubes? How many tubes were drawn? How were the tubes handled after the draw? Did someone turn them upside down and back up, and how many times did they do it? What happened to the tubes after the draw? Did they go to a lab or did the cop take them? Look around. Is there a video camera visible in the room? Your attorney will want to know these things.
There is nothing you can say that will help your case, and lots of things you can say that will hurt you. The police are not going to have a sudden change of heart, apologize and un-arrest you. The same goes for the hospital people. Nurses see cops at the ER all of the time. They usually like cops. If you chit-chat with the ER people it can only hurt you. Shut up. Don't say anything. The only exception is that some states require you to affirmatively state that you will take a test. In those states say "yes" and then shut up.
Hire a DUI specialist
DUI cases are very complex. The science alone is beyond most lawyers. You need someone who knows their way around a DUI case, and knows it well. The National College for DUI Defense, Inc. is a good source for skilled DUI defenders. Their site is listed below.