There are several rules about credit transfers. First of all, you must attend an accredited institution to expect any credits to transfer. Next, every school has a limit as to how many credits they will accept in transfer, and that's based on their credit system, not the one at your college - so if they say they take up to 30 credits, and they count each class as 3 credits, that means they'll take 10 classes no matter how many credits those counted for at your current college. Finally, you need to have a minimum grade (usually a C or better) in the class for it to transfer, and the new college also needs to offer that course (so intro physics would almost certainly transfer but a nursing class won't if the new school doesn't also offer nursing).