In all SWR classes, we do a gear check on both the helmet and the PFD. The PFD should be checked for obvious signs of wear like tears and extensive fading. If the PFD is a rescue vest, examine the quick release belt for proper threading. Look for any dangling strings that might catch on something. Carabineers near the collar bone are a common safety hazard that is often overlooked. The tether attachment to the belt should also be inspected. Ideally, it should be a continuous ring from the manufactuer. Alternatively, a locking carabineer can be used (never a non-locking carabineer). Finally, pull firming on the shoulder straps to ensure the vest is secured snugly.
When I check a helmet, my main concern is fit. I like to test for rollback with two fingers lifting on the brow above the forehead. If the helmet rocks back more than a half inch with light pressure, it is far too loose. This is a very common cause for concussions. Another useful test is the Leroy Jethro Gibbs (NCIS) head slap on the top of the helmet. If that really smarts, chances are the foam isn't thick enough or has little or no give. No travel in the foam along with a stiff shell transfer the shock load to the neck (or head as well). Don't hit the head too hard or better yet, have the student smack the top of their helmet themselves. Better to discover this way than when you flip and hit a rock at speed.