Just make sure you are relaxed when you go into the on-the-water evaluations. I did CYA and not ASA, but it's the same idea. I saw instructor candidates who weren't successful, I think because their nerves got the better or them, or maybe they were hung over. They blew gybes, crashed gearboxes with high rev shifts, really amateur stuff, and were told to come back when they had more time afloat. If you can get some extra time to do some docking in tight spaces, do it. Our IE had us doing dockings in ridiculously tight quarters with a strong cross-wind, and I saw some pretty tightly clenched teeth...
Other than that, loosen up and have fun with the clinic, and take feedback as being positive - depending on the IE, they may try to rattle you to see if you can take stressful situations. In the classroom presentations, keep it simple. A couple of guys wiped out in the classroom side because their presentations were overly complex, and incomprehensible.
So have fun, stay loose, and keep it simple.
I'm taking the ASA Instructor Qualification Clinic (the first three levels -- Basic Keelboat, Basic Coastal Cruising, Bareboat Chartering) later this month. Am curious if any of you have advice on what I should keep in mind or prepare or any feedback on the experience.