be polite to the barn you are leaving from and do your research when moving to a new barn!
Be very open about the move to your previous barn owner and boarders. Just make it very clear and try not to cut any ties.
Make sure you know a lot about the barn that you are switching to and they can teach you what you want to know. Don't be afraid to tell them what you do and dont know and ask questions if you need to. They might start you of simple, but just be patient because eventually they will be teaching you and the right skill level and pair you with the right trainer and horse! Good Luck at your new barn!!