Hi there! My son was diagnosed at age five with ADD/ODD. From this point on, keep detailed records of every piece of paper, prescription she is given, medical records and so forth so you will be fully armed with info when you go to different doctors. It's a good idea to keep a diary of her behavior, appetite, sleep patterns and if they change when she is given new medications also. My son has tried so many medications, I can't keep track of them, save for the diary I have kept. Don't get frustrated (easier said than done!) when you go from doctor to doctor and you have to recite the entire life story up until that point for your daughter and what has been going on with her. I pretty much know my son's verbatim, HAHA! If she is in Kindergarten, you may want to ask her school about the possibility of getting an IEP (Individualized Education Plan) for her also, if it's feasible. There are also Behavioral IEP's too. Those can help you and your daughter's teachers figure out the best way to accommodate her needs at school. This will also open the door for a school counselor to help you along the way.
Some good books to read are the ones already mentioned by some of the fine folks in here, and I also recommend 'From Defiance To Cooperation' by John F. Taylor, Ph.D. and 'The Challenging Child' by Stanley I. Greenspan, M.D. Most of all, keep your wits about you and try not to let your daughter see you sweat (again, easier said than done!) ODD kids seem to look for cracks in their parents' armor so they can exploit their weaknesses! Best of luck to you, and keep us posted in the coming weeks!