So, what might your flight instructor pull on you to see if he or she can catch you off guard?
One of the deadliest pilot killers is complacency. And one of the places where the pilots get most complacent is on the ground, during the walkaround. It is after all, a tedious, repetitive thing that rarely reveals anything wrong, so it's little wonder that many students, as they get further along in the flight training and more confident in the airplane, get just a tad sloppy on the pre-flight.
The number of things instructors can do to check if you're doing a thorough pre-flight is practically limitless, so I won't even attempt to list them all. But just to give you an example, a common (and, what's important, safe) way to check if a student is paying attention is to pour a bit of oil or hydraulic fluid near the plane or scatter a few rivets, and see if the student brings it up as a concern. Another instructor used to place an empty coke can right in front of the air inlet of the engine cowling -- and he says it was frightening to see how many students complete missed it sitting right there in the open.
One: know your systems. We're not mechanics, just pilots, but a basic understanding of what different parts of the plane do will help you do a more thorough and meaningful pre-flight check.
Two: imagine scenarios. At every point at the walkaround ask yourself: "What can go wrong here?", then visualize what that might look like, then check to see it doesn't look like that. It doesn't help to "make sure everything is okay". Be specific, tell yourself what you are looking for. For example, when checking the right landing gear, you might tell yourself you're looking for: possible hydraulic fuel leaks, tire wear and bold spots, low tire pressure, frozen brake pads, worn out brake pads, rusted out brake disks, chocks or other obstructions that will be invisible once you're inside the plane ready to start... When checking fuel, you're checking for the wrong colour, the presence of dirt or water, the fuel levels, fuel drain leaks.
Three: pretend you're an instructor and see how you could try to trick your student -- will you pull out the plane's registration? stick the plane into a corner out of which it cannot be taxied safely and see if the student realizes this before starting the engine? Anything else? Let your imagination run wild and give you scenarios no instructor would dream of doing in real life (such as intentionally contaminating the fuel, cutting the alternator belt or deflating the tires) -- and then defend against those tricks through thorough walkaround! :)
In real life, emergencies often strike when you least expect them -- and your instructor should do his or her best to imitate real life in the advanced stages of emergency training. Not only might you get an emergency with no warning, your instructor may attempt to distract you first, just to be really mean (or really nice, since it could save your life one day).
Trick: without warning, and possibly with during some distraction, the instructor will pull an emergency on you. The most common one is, of course, engine failure. Airplane engines these days are very reliable, except, it would seem, when an instructor is on board -- then they seem to fail every other flight. ;) Showing you a "40-million dollar mansion" down below, or "this really cool dirt bike race track" and "accidentally" ending up in a spiral dive is another favourite.
Expectancy is when the air traffic controller says "taxi alpha hold short runway 15" an you hear "taxi alpha, cross runway 15" because this is what you've heard every single flight until this one. It's assuming something is a certain way because it's always been that way before.
I once was in a plane with a student who misheard the above-quoted instruction. After he read it back incorrectly, the controller said it again -- and the student misheard and read it back wrong again the second time too! He didn't even realize he was being corrected -- he wondered out loud why they kept telling him the same thing twice, even though he read it back fine the first time! That's how dangerously powerful expectancy can be.
To put it bluntly, expectancy can kill.
This sneaky trick is somewhat a reverse of the previous: your instructor may try to fool you into expecting one thing and see if you fall into this trap.
Antidote: Never. Assume. Anything.
Always expect something to go wrong or at any rate to go differently. It's easier said than done, but a good instructor will help you. Not in a small part by sprinkling tricks like this throughout your flight training!