I learned a lot by watching electricians work on things I needed done. Same with plumbers and cable guys.

It really saves a ton of money, because then you can just do it yourself. Like replacing the dimmer switch with a regular switch - costs about $2 from the hardware store for the switch, and a few minutes.

Having a plumber show up costs $300 just for him to come to your house. It pays off big time to do what you can yourself.

P.S. I always ask for permission to watch them work. They appreciate the ask, and so don't think it's creepy.