It's important to note that no two clients will move the same and that when they first start working with you, certain aspects need to be taken care of first before exercise presciption can be progressed.
The top 5 issues that I see on a day to day basis are listed below:
1. Lower Back Pain
2. Forward leaning posture and curvature of the upper back
3. Tight Hip Flexxors
4. Shoulder Pain
5. Knee Pain
All should be dealt by looking at both the joint below the issue, as well as the joint above the issue. Proper exercise prescription should always work the client back in to a proper range of motion first, and then strengthen up the range of motion from there.