Organize your time. Make a list of all the things you need to do. Start with your class schedule and add in your work schedule. Then allow time for studying and socializing and add any other things you need to do. Buy a calendar or set up a calendar on your computer. You can also use your phone for reminders.
Enter the information from your list either on the calendar you bought or on your computer calendar. It is easier if you can do it on your computer especially if you are spending a lot of time on it, because you can put in reminders so you aren't late for anything.
Settle conflicts. If you have conflicts in your schedule, you have to decide which is more important. Obviously, your top priority is your classes, so you have to reschedule or cancel anything that conflicts with a class. Work should be your third priority. First being your classes, second studying and doing the work for your classes and third work. After that, the priorities are for you to decide.
Talk to your boss if your work conflicts with your schoolwork. You need to find a job that will let you work around your schoolwork, which includes your classes and preparation time for the classes. This may mean having a different schedule every week or just working weekends.
Keep a close eye on your calendar. No matter which method you are using for your calendar, whether it is paper or computer, you need to watch it carefully so you don't miss anything. You can also put reminders on your phone so you don't miss the most important things that you need to do.