The days right after
The shock is ordinary, and so is replaying the stop over and over. While that settles, a few practical things are worth doing. Expect contact: the court will send notices, the motor vehicle agency may send its own, an insurer may call, and if a vehicle was towed the lot will want to hear from you promptly. Letters from attorneys you have never met often arrive as well, because these records are public, and that is unsettling but not a sign that anything unusual is happening. Sort the mail instead of avoiding it and keep all of it in one folder, envelopes included, since postmarks sometimes matter. Almost none of this calls for a decision from you right away; what it calls for is that nothing gets lost or ignored.
Write it down while it is fresh
Memory for an evening like this fades faster than people believe it will. Write the sequence out for yourself: where you had been, what and when you ate, what you drank if anything, the route, why you were stopped, what was said, what you were asked to do and in what order, whether anything appeared to be recorded, and how you felt physically. Note the weather, the road surface, and what you were wearing on your feet, since roadside exercises are affected by all of them. List anyone who was with you or saw any part of it, with phone numbers. Keep these notes for us rather than posting about the arrest or discussing it in messages. Details that seem irrelevant to you are often the ones that end up mattering, so write down more than you think is useful.
Two processes start at once
The criminal case and the license side generally begin moving at the same time, are handled by different authorities, and can reach different outcomes. People who attend to only one of them are usually caught out later by the other. A first matter is also assessed on its own facts, so what happened to a coworker, or what you read on a forum, tells you very little about your own situation. Bring the paperwork, your license, and the notes you wrote to our first meeting. We will walk you through what is actually in front of you, including the parts that turn out to be routine. You are not the first person to sit in that chair, and the process is usually more navigable than it looks from the outside.