The Maiden Flight
A little prevention can remove the worst parts of a maiden flight by thoroughly checking the plane on the ground first. Get that main wing off and look over the radio and pushrod installation. Is the nosewheel hooked up backwards? Any flex in those nyrods? Excessive throws on the control surfaces? Usually 1/4" to 3/8" on the elevator is plenty, as is l/4" on the ailerons.
Can the battery pack be moved to correct for a center of gravity balance point that is off? With the main wing back on, is there any noticeable warp in it? Finally, help the student get that engine running decently. That means good and rich (cracking back and forth between two and four cycle) so it breaks in properly on the top end; and a reliable idle setting on the bottom end. If the idle is giving you trouble, you can skip it on the first flight as long as the engine will idle slow enough to allow you to land at will.
Okay, now for the crucial lift-off. What kind of airfoil on the main wing? If it is a flat bottom (which it should be for a student), you must remember that the rudder is more effective than the ailerons. So if the nosewheel is off a lot and you hold right rudder on the takeoff roll to keep the run straight, the moment the plane lifts off it is going to try and do a snap roll to the right and cartwheel back to earth.
Using left aileron may not overcome the right rudder, because the ailerons are less effective than the rudder, especially near stall speed.
So either stop the takeoff run and get that wheel straight, or be ready to get back to neutral rudder the instant those wheels leave the ground. if the nosewheel can't be readily straightened, and you don't feel comfortable getting off the rudder at lift off, try a hand launch. But tell the student to throw it level or even down a bit, to avoid the inevitable urge of students to "help" you by throwing it upward (right into a stall). (They never will have the courage to throw it downward, but by stressing downward, they might at least let it go level. Maybe.)
You are airborne. Whether by rise off ground or hand launch, make your climb-out shallow. You can better fight off a warp at a shallow angle of attack than you can in a steep climb that is near stall. Make no turns until you are well up in altitude. Just keep climbing straight out. Now concentrate on that straight climb-out and on what you are doing with the control sticks. Are you holding right stick and pulling back on the elevator. You'll be surprised how unconsciously you'll hold in corrections, but if you relax at too low an altitude, the plane may suddenly respond by diving and rolling right, using our example above.
Once you have gained altitude and suspect that trim changes are in order and what they might be, make the trim adjustments.
If full down trim won't produce level flight, don't stay up long because as you burn off fuel, the tendency to climb will get worse. Get a fix on any other trim adjustments, make them, and then bring it back in so the control linkages on the plane can be adjusted to bring the trims on the transmitter to neutral. Force the student to make those linkage turns while you stand there, or else next week they still will not have been made. If you think a maiden flight is scary, wait until you take one up that was successfully flown the week before, but has the trims out of whack on the transmitter because the student (or you) bumped them. You can only guard against that by moving all trims to neutral just before the takeoff roll