There are certain strategies that wheelchair users can employ to lower the risk of shoulder pathologies. Most of these strategies are fairly straight forward and feasible.
1. make sure your wheelchair is configured properly. An occupational therapist could check this for you. A properly set up chair will decrease the forces and strain require to propel your wheelchair. Adjust the rear axle as far forward as possible without making the wheelchair too unstable. This will allow you to use more of the wheel without having to reach way behind you to grab the rim.
2. try to get the lightest wheelchair possible, with tires with the lowest rolling resistance. This will make a huge difference when propelling up slopes.
3. learn the proper stroke! use long strokes rather than small frequent ones. Allow your arms to recover naturally after a forward stroke. Don’t jerk the arms back.
4. During transfers, vary the arm you lead with to distribute the load.
5. Flexibility and resistance exercises! These should target the shoulder girdle (rotator cuff, pectorals, etc.)
More information here.