Plan your class and work schedules as far ahead of time as possible, in order to avoid time conflicts.
Arrange your classes so that you don't have to go to campus more than once a day.
Use time efficiently. Use those 10 minutes spent waiting on the phone to read a few more pages. If your job has a lot of downtime, use the opportunity to do schoolwork.
Be flexible and willing to make sacrifices; you'll probably have to cut down on both work and school to make this work.
Inform all your professors, teaching assistants and employers about your situation, so that they can be flexible as well. Keeping them in the loop is the best way to keep them on your side.
Contact the student services office at your school. The professionals there will have advice that fits your particular circumstances.