Well, once upon a time I was a drafter for an architect, and I worked with construction workers out in the field. I had to wear a hardhat.
What I would have told myself back then was --- be you! Don't change up who you are to fit into the group. Be safe. Always wear the hardhat, no matter what when you are out in the field. Take care. Listen to your body. Ask for help - do not be the hero on the job. Ask questions. That's how you learn. If it's going to take an extra 10 minutes to make it safe, take the extra time to do it!
If you are headed to a union meeting for the first time....be open. Listen. Ask a question or two to be seen, but listening is key. Find out who is a good worker and who is not, and stick with the good workers.
Listen to yourself.
Keep track of your tools - write your initials on them. Never take someone else's tools....if you accidentally do, be sure to get it back to them. Keep rude jokes out of the workplace. Many more women are in construction these days, and we do not like the sexist jokes.
Don't say yes when you want to say no. Work hard and smart. And don't let the job take over - live your life, be with loved ones, keep a balance.
Angie has great information and she is totally correct in saying be yourself. The union can be as great as you want it to make it. I have a lot of friends and colleague's in the union and some have been in it for years.
One thing I do think is an important benefit, is utilizing the union for everything they offer. They have multiple levels of training opportunities that you can take advantage of. Along with those opportunities the way they train and advance the levels in the union is a great way to actually become better at your job while learning on the job.
Best of luck