Trades apprenticeship applications open in Boston - what worked for you?

I heard of an apprenticeship with paid on-the-job training for people changing careers. Any experience at all would help. Classes are in the evening and work is during the day. 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.

Thanks for writing this out. I went through something close to it 7 months ago, and it settled down once I kept a simple log of every call and form.