Apprenticeship openings for electricians and welders - first time posting

The training centre near Denver opened applications for apprenticeships in electrical and welding trades. I do not usually post, so bear with me. The application needs a diploma or equivalent, a driver's licence and a short aptitude test. What do you wish you had known?

The aptitude test was mostly maths and reading a diagram. Free practice tests online were enough for me.

Keep everything in writing and save the confirmation numbers. It saved me later.