Like others say, read up on medical terminology and anatomy&physiology if you can.
Once class starts pre-read the book. Ask questions early and often, the most important question being "why?" Volunteer for demonstrations. When doing practicals and scenarios don't rush but think them through and learn them the book way, you are tested on the book way. Way more important to do procedures correctly than with speed.
Do uncomfortable things, find out what you like, have fun with it.
I agree on reading ahead, but I wouldn't pre-read the whole book, it can get confusing until you can put it all together.
Don't be afraid to ask tons of questions and like someone else pointed out you will have people that don't care in class. Frequently you will have repeat students that couldn't pass and are there again and often it shows why they are taking it again. Try to ignore them and do your own thing, focus in on the ones that are doing great and work with them. They will push you to do better and won't just be hoping they get out early.
For me the workbook was a great tool also. I would read the chapter, do the workbook and then correct it, if I got something wrong I'd write the page number and go back and review what I got wrong. The workbook will reinforce things in the text that you think aren't important and would have skimmed over while reading.
Practicals are a big thing, it's easy to sit in the back of the room and watch everyone else do them, be one of the first to stand up and volunteer, often you will get more out of the instructor because they aren't getting tired of them if you are first and then you can sit back and watch the other ones and pick up on things you can do differently or better. In my AEMT class I had the most sticks in class, when there was a chance I didn't hesitate to say hell yes and do them. I ended up with a great rate and have been successful because I jumped right in and built my skills.
Same thing when I had to do clinical time, I made sure I stayed busy, I didn't wait for someone to tell me to come along, I was like a lost puppy and followed them when they went to get a patient, if I heard of something different being done I jumped right in and watched or helped. I also didn't stand around texting or playing with my phone. If I needed to take a call or call someone I would let them know it was coming and why, then I would go to the nurses break room for the call, then come back 100%. If it wasn't busy I would clean, look at equipment, re-stock the IV trays, anything to keep busy. I got complimented by more than one nurse who recognized that I was the only one to re-stock supplies and when they needed something done they would go out of their way to find me to let me do it.
Forming an alliance or study group will help. We often got together outside of class and discussed lectures, ran ideas back and forth or went over practical stations. It wasn't always hands on, frequently we would do a sort of round table discussion about the skills stations and it helps to memorize the sheets so when you test, you remember the steps and what to do.
If you aren't affiliated with an agency, try to get a local one to let you hang around. It is great to be able to discuss difficult topics at length and with someone who has a different way of explaining things. Plus if you get to see things done that you are learning it helps.
You get out of it what you put into it. It's endless and only the beginning when you take your first class. No one person knows everything, but it's good to be well educated on what you are supposed to know.