Be aware of your best ways to retain information. It's common nowadays to take laptops right in the classroom and type away taking notes or even using recorders. Some students will just keep those notes or recordings and reuse them when it's test time. But many students and even those of us in the working world, find that transcribing your notes again after the class is a positive way to reinforce what you heard in the lecture or classroom. It also enables you to perhaps catch something you may not understand, but hurriedly typed down or just passed over listening in the class.
As other noted, in taking advantage of professors or TA's hours, those gaps in your notes can be a good talking point to discuss lessons and assure you are grasping the key points for the course. You can use the notes and findings too if you are in a study group. Doing this, your aren't realizing you have gaps one day before a test.
I was also one of those, who if I could, took morning classes if available and tried to see if I could finish me classes by mid-afternoon. Not always 100% able, but it allowed me to use professor times which had a tendency to be in the afternoons and to participate in some school activities such as clubs, publications, etc. Those activities can often be a great stepping stone to future jobs and a great way to meet people.
Keep up with assignments and reading. Don't cram. As others pointed out, fill your time between classes somewhere relaxing, but do your simpler reading assignments, fine tune To Do lists, or re-read notes. Keep the information fresh and current each day. You will feel a little less stressed, more on top of your workload and find you have the time to enjoy some extracurricular activities and weekends and evenings may not be so panicked filled. Can't emphasis enough how being organized in college can make all the difference.