I can think of a few things right off the top of my head. I'm sure others can come up with plenty more.
First, the school did you a dis-service by not covering the area. Liability is a poor excuse to skip an important safety issue (BTW, they can be held liable if they failed to teach you something they were supposed to and you got hurt because of it).
Be that as it may, there are a few ways to help prevent injuries.
1. When you lift, keep the load as close to the core of your body as possible and your back as straight as possible.
2. While keeping your back as straight as possible, lift with your legs.
3. While carrying the load, do not twist your body. Turn your whole body as a unit. This prevents torsion on the lumbar discs which are very strong in compression but not very strong in rotation. Twisting while bending is the most common cause of traumatic lumbar disc herniation.
4. Communicate with your partner. Injuries very often occur when one partner does something that the other is not expecting nor prepared for.
5. If the patient is just too big, call for a lift assist!
6. Mentally plan each lift. Do not lift mindlessly. Take half a second to think about what you want to do and how to do it most safely.
7. (or is it number 1?) Remember the ABCs: Ambulate Before Carry. If the patient is walking when you get there, keep them walking right into the bus! Note: this doesn't work for the 20% of calls that you do which are legitimate (chest pain, respiratory, CVA, trauma, etc). Those you have to carry. It does work great on most (not all) of the other 80% of calls which are often BS.
These have worked well for me. I'm interested in seeing what others say.