Union apprenticeship sign-ups near San Diego - what worked for you?

I heard of an apprenticeship with paid on-the-job training for people changing careers. I do not usually post, so bear with me. Classes are in the evening and work is during the day. What do you wish you had known?

Bring your transcripts and any proof of work history. They asked for both in the interview.

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