There are lots of advice, but I'll contribute to it. I have been teaching for a few years and I was a good student before that. So I guess my advice are meaningful.
1/ SLEEP and HEALTH! Sleep is critical. Health is critical. Plenty of people apparently already pointed it out. But your body and your brain do need the sleep. Getting 2 more hours of sleep is typically more important than getting 2 more hours of study. Also, you will sleep better if your optic nerve is not too stimulated before you fall asleep. So try to stay aways from screens in the last hour of your day.
2/ Beware of slides. Many classes are slide based nowadays. I find it idiotic in most topics. Slides are typically short bullet points, they won't help you remembering everything. Also they contribute to student not writing during the class. Most people have a visual memory which means that you need to SEE the material. Also you learn better when you are active rather than passive. Most of the time you can accomplish both by writing your class.
3/ You need to study in the calm. No TV or radio in the background do not help you study, they are likely to be distracting you. Music can be helpful to cover background noise, I'd stay away from high BPM tracks or tracks with understandable lyrics. Classical, instrumental, electronic or pop music in a language you do not speak are typically good candidates.
4/ You need to study smart. Typically I find that going over notes, correcting them or re-writing them helps a lot to get the data in. I tend to spend at least 30 minutes per hour of lecture. Making picture illustration (schemas) helps. Before a test, I usually try to make a 2 or 3 pages summary of what is important. Once again, the point is not to have it, but to make it. Doing extra exercise help.
5/ Out of class material. The way the informations are presented in class is not the only way to present the informations. I found it extremely useful in the past to pick other sources of informations. Go to your library and pick a book related to what you study and read it when you have time. It might say the same thing as your class in a different way, or just say something different. But for sure that will help you getting different perspective of your subject.
6/ Exercises. There is no secret in how to deal with exercise. You need to do exercise. If you are too slow, you need to do more. It might be important to understand WHY you are slow. Do you not understand the techniques involved? Or does it take you too much time to apply them?
Finally remember that going to college is essentially a full time job. Even if you are enrolled for only 15 credits, it should probably take about 45 hours of your time each week.