How do I spot subtle movement compensations in clients?

You can assess movement now, and that is a solid foundation. The subtle compensations hide because the body is clever at covering its own weaknesses. It borrows from one place to protect another, quietly, so the flaw looks like normal motion. Seeing that takes an eye trained over many bodies, not just knowledge. The way you sharpen that eye is volume and attention. Watch more people move, and watch the same movement from more angles. Ask what a joint is doing when it should be still, or where the effort goes when one part is weak. Compensation is the body solving a problem, so look for what it is trying to avoid. This week, pick one common movement and study it in ten different people. Note the small differences you would once have missed. You are not lacking some gift the experts have. You are building the pattern library in your eye, one careful observation at a time.