In my off-season manual, I allude to several performance tests that I feel best demonstrate potential for athletic excellence. As a tag along to this, I've noticed several non-physical behavioral "tests" that show me an athlete is psychologically ready to commit to success. These issues are especially common in our high school athletes.
1. On the diet front, we ask our athletes to bring us two-day nutrition logs (one training day and one non-training day) so that we can evaluate how they can improve their diets. The more dedicated athlete, the sooner we get that back (if at all).
2. Also on the diet front, aside from those who are lactose-intolerant, athletes who complain about the taste of cottage cheese just never seem to "get it." These same individuals are usually the ones who dislike every flavor of protein powder imaginable.
3. Motivated athletes realize that if they fall off the wagon by eating some junk food, the entire day isn't "lost." They get back on track and call it water under the bridge. Less motivated athletes tend to just consider an entire day a way and have another bag of Twizzlers and a two-liter bottle of Coke.
4. One's response to injury is also always a good indicator of how bad one "wants it." The best athletes want to train through the injury - even though we don't advise it, obviously. With these individuals, we're big on showing them what they CAN do rather than just reaffirming what they CAN'T do. The idea is to continuously challenge them with movements that either a) allow them to train around the injury and b) movements that will help to rehabilitate the injury and/or prevent it from occurring again. The softest of the bunch usually skip the session because they want a pity party.
As much as a stereotype as it may seem, my experience with female athletes in particular has been that injuries tend to lead to complete abstinence from exercise in favor of partaking in slumber parties with Ben and Jerry.
5. Some exercises - deadlifts, squats, single-leg work - are flat-out challenging. I love it when guys show up to the gym absolutely ready to get after these movements. It drives me crazy when guys only get pumped up for bench day, and would jump at the chance to miss lower-body training sessions. The more you learn to love an exercise, the faster you'll improve with it.