While I don't think parents are expecting step-by-step instruction on how to throw or hit, my plan for our upcoming tryouts is take a few minutes at the very start to review what it is I'm looking for / what we teach - throwing as a continuous motion, butt up / chest down when fielding grounders, timing / moving BEFORE the pitch is released, etc.
If they struggle with those concepts, that's OK, b/c I'm not looking for them to have already mastered the skill. It's more a way to determine "coach-ability" - are they willing to try to incorporate what I'm showing them with what they already do or know?
As a parent, this is what I am looking for at a tryout. I want to see coach interaction with players. I want to see them interact with my DD as well as observing how they interact with other individuals and the group as a whole. I don't expect a coach to fix my daughter in the 3 minutes he sees her at a tryout, but I do what to see him coach in the brief amount of time they have together. Just give me little bit of how you coach so I can evaluate if my DD fits with your team.
The key for me is, you are trying to sell yourself and the team as much as find the kid that best fits your team.