Determine what type of learner you are. You may learn more easily by watching, by listening or by doing. Try to learn by the method that's best for you. Make sure you rarely miss class, and ask your teacher about anything you don't understand before moving to the next concept.
Most students are visual, auditory or kinesthetic learners. Visual learners learn by watching a teacher perform a math problem; auditory learners learn by hearing a problem and its solution described; and kinesthetic learners learn by doing the problems themselves. Try to learn a couple new math concepts by each of these methods to see which works for you. If you are a visual learner, pay attention in class and watch carefully when your teacher is demonstrating problems. If you are a kinesthetic learner, try to work the problems alongside your teacher to see if you get the same answer.
Math concepts build on previous concepts, so you can't skip anything. If there are any concepts you don't understand at first, ask your teacher, a friend or a tutor to help you before the class moves on to the next concept, or the next part will be even harder. Try not to miss class, and if you do, ask for help to catch up before moving on. Keep up with homework assignments as they are given to you so that you don't fall behind.