The first step is figuring out where your problems are. No one else can figure that out for you, and if you don't honestly attempt your homework, you'll never know what you can or can't do. Someone else can help you learn the material, but this process is much more efficient if you already have a list of questions or topics that you need help with.
Many teachers want you to do things "their way" so it's important to have clear, complete examples in your notes from which to study. We have all had a teacher who refuses to give credit for having the right answer, but the wrong form, or method. Instead of getting into a power struggle, and getting on your teacher's bad side, learn what is expected of you and use that as your model.
Many students struggle on tests because they learn to just look at the "math part" of the question and go on instinct. They do not actually read the question, often because they wouldn't really understand the words in the question anyway. When studying, pay particular attention to the wording of questions. Learn what is of expected of you when the question says, "Simplify" or "Evaluate." Most students don't realize that sometimes half the questions actually tell you exactly what to do, if you just understood what the instructions said!
One of the biggest mistakes math students make is thinking that they should be fine because they did the assigned homework. Most students are not adequately prepared for tests if all they've done is keep up with the homework. You may be glad at first if you find yourself with a teacher that only assigns a handful of homework questions per night, but these are exactly the students who wonder why their marks aren't higher. You must continue to do questions -- even the ones your teacher didn't assign -- until you know you understand it. Otherwise, you're just fooling yourself.
It's easy to focus on one kind of question at a time, but you have to learn how to do questions when they appear in any order. One helpful strategy is to write out several different kinds of questions on separate index cards. On the back, work out a full solution. When studying, reach into the pile and pick a card at random. When you can successfully complete any question you pull out, then you know you're ready for a test.
Will tests be based on questions from the text book only? Which topics will be covered on the test? If you don't know, ask! Warning, you do run the risk of sounding like one of those annoying students who isn't interested in something that isn't on the test. Unfortunately, though, you have to do whatever it takes to get the best marks possible, and studying the right material is a part of earning the highest marks possible.
It's good to ask questions, but you should also try to give answers. It's good practice, and teachers will appreciate your efforts.
Often teachers know which topics are hard for students, and they might have extra handouts or resources for just such an occasion. This feedback can also help the teacher see which topics they might need to spend more time on in class, or might need to explain in more detail. If no one speaks up, then the teacher won't know there are problems.
Many teachers are happy to offer extra help, and are happy that you care enough to spend extra time outside of class. Sometimes you might learn even more, such as which are likely test questions, because teachers can let extra information slip (often without realizing it) in extra help sessions. Subconsciously, the teacher may give out helpful information. And, when it comes time to marking your test, your teacher may also be subconsciously "pulling for you" because of your efforts outside of class, and they might give you the benefit of the doubt when marking.
The first few days of class can seem so easy that you might think that you don't need to get serious just yet. But, this is your opportunity to get into good habits, when they're easy enough to keep. You might even try reading ahead a bit. Make good use of your time in the beginning because you'll be wishing you had it back later in the semester. Of course, if you didn't get off to a good start, decide to get back on track right now. Better late than never.
If you're not writing anything down, you're not really studying. We always say that to prepare for a test, you should practice doing exactly what you'll be asked to do on the test. If you had a piano exam, you would practice your pieces over and over again, not just stare at the sheet music saying, "Yeah, I know that." The same goes for math.