Coupling and Uncoupling
Coupling and uncoupling questions reward exact sequence and inspection habits. When coupling, inspect the fifth wheel and apron, back until the fifth wheel just touches the trailer, get out and check alignment, then back firmly so the locking jaws close around the kingpin. Do a tug test in a low gear against the trailer brakes, then visually confirm the jaws are closed and the safety latch is over them, connect the air lines (emergency/red first, then service/blue), and raise the landing gear fully. Traps: questions that place the air line connection before the tug test, or that treat the tug test as sufficient without a visual check.
When uncoupling, park on firm level ground, apply the parking brake, lower the landing gear to the ground, chock the wheels, disconnect the air lines (service first, then emergency), pull the release handle, and drive slowly out from under. Expect questions about the kingpin (the pin on the trailer apron the jaws grip) versus the fifth wheel plate, and about why you should not leave the trailer resting on the tractor after pulling the pin.
Rule of thumb: never trust a single indicator. The coupling is secure only when the tug test holds, the release handle is in, the safety latch is over the jaws, and a visual check shows the jaws closed around the kingpin.
Also know that a high hook (tractor backed too far under a trailer) can lift the trailer and damage the landing gear or tractor - check that the trailer apron sits flat on the fifth wheel.