I'm an eight year member of the
United Association of plumbers and pipefitters and will likely stay with them until I can retire. I'm not sure if things work differently in the US but basically if you want to join a union then look up the nearest local and stop by to introduce yourself and see if they are accepting apprentices. You may have to write a test, do a drug and alcohol test then wait for a call and you'll get on as a first year which is basically a helper and you'll learn the basics of the trade and eventually go back to school and write some tests then become a second year. You do the same thing for 3-5 years (depending on the trade) and eventually become a journeyman. If you can't get on with a union shop (it can be difficult) then knock on some non-union doors to see if you can get an apprenticeship started. Another way in would be to take a course at a local vocational school
Most of my friends are tradesmen too and we live pretty decent lives, especially us that worked in Alberta during the oil boom, I've run into more than a few legit blue collar millionaires. Then again I know a lot of guys who blew all of their cash on hookers, blow and big trucks too. Here's some specific advice I can give on the trades:
Pick one you can see yourself doing for 5-10 years: Check out some Youtube videos, call a local contractor and see if you can stop by a job site for a visit, call the union, etc. You will need to work for at least 5 years
"on the tools" before you can advance or start your own business. Contrary to popular belief, just because you begin a trade, it doesn't mean that you'll be doing manual labour for the next 30-40 years. On commercial/industrial job site, the advancement ladder looks like this:
tradesman-foreman-general foreman-superintendent
There's a lot of other related jobs that aren't on the tools which you could get into such as safety, QA/QC, planner/scheduler, dispatch, etc. Really its up to you but having a journeyman ticket in a trade can open a lot of doors, if you take night classes or online courses and get a degree in management then you could get into the office pretty easily.
Pick a trade that works in a variety of industries: Electrician and plumber are two of the best since you can work in residential/commercial/industrial so if one sector slows down then you can just bounce to the next. I have a few buddies who started out wiring houses as first year electricians, then moved onto office towers and finally ended up in the oil sands doing heavy industrial work, they are well rounded tradesmen and when they aren't working up north, they wire people's houses for cash. Unfortunately a pipefitter, millwright or industrial insulator won't find work in the residential sector, which is non union anyway.
Move to where the work is: I'm not too familiar with the markets in the US but pick your destination wisely, you want to go somewhere busy so you're not sitting on your ass too much waiting for a call. Find out where there's a housing boom going on, where they're putting up lots of office towers/arenas/infrastructure or where there heavy industrial expansion going on. The union websites are a good place for this.
Work Safe: This is priority #1, people get killed and injured on job sites every day. Union companies tend to have better safety records but shit happens everywhere, no amount of money is worth losing a limb or your life, so pay attention at all times and always wear proper PPE.
That's about all I have for now, I've been at this for almost a decade now and I still like working in a blue collar environment where I can act like a man and not have to worry about being politically correct at work. It's a lot of fun too, a job site is like one big locker room where a bunch of men scream and yell all day, tell jokes and bust each other's balls non-stop, if you have any other questions just let me know.
UNIONS:
Electrical-
http://www.ibew.org/
Carpenters-
https://www.carpenters.org/Home.aspx
Operators-
http://www.iuoe.org/
Iron Workers-
http://www.ironworkers.org/
