This is the best advice I can give : http://www.khanacademy.org/#physics for physics. http://www.khanacademy.org/#calculus for calculus.
Know your math. So many newbies set up the problem fine, but then struggle to get to the end of the problem because they can't solve for X, for example. Do a *lot* of problems. Some students make the mistake of thinking that if they choose to be a physics major, then they should be just naturally good at it. Wrong. It's hard, and it takes an incredible amount of time and practice. (Sure there will be that occasional oddball who seems to just "get it" out of thin air. Disregard them; just focus on learning the stuff.) Realize you will get stuck - often. Don't let it trouble you. Work on it for a while. If you can't get it, take a break. Move on to the next problem, and come back to the one you were stuck on later (maybe the next day). Ask for help if you need it. Don't get discouraged.