Hi A.,
I spent many, many hours in math classes (since my degree required 24 hours of math and another 12 in physics, which is nothing more than applied math), and I am by no means a math whiz. I found that four things are essential to being successful:
1. Stay in close contact with the teacher. They may offer help in an area that you are struggling in, but this contact will also help them to place a face with a name. They will be more likely to help you out at grade time if they know who you are and they know that you are trying.
2. If there is a TA or a tutoring service, take advantage of these services and get some help. The more time you expose yourself to the subject, the better you will get.
3. Most importantly, you MUST spend time working problems. If you struggle in math, which you indicated that you do, you need to work more than just the assigned homework problems. The only way that you will get better is to constantly practice. Math skills are not learned through memorization, they are aquired by practice. If you run into problems that you can't figure out, ask your teacher or TA or tutor to help.
4. Don't procrastinate! Get your homework done early so that you can get help if you need it. And don't wait until the night before a test to begin working problems. Practice as often as you can, regardless of when your next test is.
I learned these things the hard way. I had to re-take a couple of classes because I thought I could simply "look over" my notes from the class to study for a test. Once I figured out that working problems was the only way to really learn the material, I was successful. I didn't make "A"s, but I did pass and graduate. Hang in there, you can do it!