Start a 401k or some other investment plan NOW.
Dating or marriage, make sure you are both on the same page about money, relationship boundaries, politics, sex, and expectations from your spouse that they will be on your side no matter what in public, and fight/discuss it later privately if you disagree.
In a job offer negotiate the best salary you can get, signing bonus, 401k matching, and severance agreement.
Pay more for anything that comes between your ass and gravity/the ground: mattress, car tires, shoes. Keep your childhood friends as long as you can, when you're older it's harder to make friends and harder to trust adult strangers.
Don't lie. People are smarter than you think.
At work dress like your coworkers, a workplace is like a tribe, you don't want to stick out.
Ignore what movies and TV shows you what "real life" is like. It's not going to be like Sex and the City for women or Spring Break for men all the time, and that's a good thing. It's OK to be traditional, in fact it's better than degeneracy.