Apprenticeship openings for electricians and welders - any advice?

I heard of an apprenticeship with paid on-the-job training for people changing careers. I am in St. Louis, in case local advice matters. The application needs a diploma or equivalent, a driver's licence and a short aptitude test. What do you wish you had known?

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

Thanks for writing this out. I went through something close to it last year, and it settled down once I kept a simple log of every call and form.