My two cents worth............
I started an apprenticeship in 1990 with the national carrier of a small country in the South Pacific, the company took on around 70 apprentices that year. Apptitude tests were carried out in bulk throughout the country, and were along the lines of 'In the sequence of shapes etc, what comes next'. I can't recall face to face interviews as it was a while ago, but I do remember the practical test. It consisted of a vertical piece of plywood with 10 holes drilled in it. The mission was to put 10 bolts through the holes with a washer each side and do up a nut on each! I clearly remember asking the instructor if it was some kind of joke, considering I'd applied for a job as fitter and turner and had to assemble a simple gearbox from a drawing at their practical test.
As previously posted it's more about how mechanically (or avionically) minded you are, are you a logical thinker, did you take practical subjects at school?
I was lucky to have a grandfather who taught me to strip and rebuild a lawnmower really early on, he taught me to use tools, to weld, and a whole lot more.
However, be sure aircraft engineering is really where you want to go. Look on this forum and you'll see airlines and repair stations going down the drain quite regularly unfortunately. I think if I was to advise my kids when they're old enough I'm not sure I could recommend aviation as a career path to go down. I've had a lot of fun, worked in some strange places, but not made a lot of money on the way. Once in the industry, it seems to me hard to get out. Looking at the job scene at the moment I wish I'd been in construction! It sure beats being in full breathing gear, in a howling southerly rain storm, on the ramp, opening the fuel tanks of a Hercules at 9pm on a Friday night!