2. Know your suit size and shirt size (not small, medium, or large). You should also know and understand the value of a tailored suit.

3. How to sew buttons back onto a shirt or jacket.
View this video on YouTube
At some point a button will fall off of your shirt, jacket, sweater, or whatever other garment. You won't be able to rely on your mom to sew your buttons back on, so make sure you know how to do it. Bonus: If and when you have kids, their buttons will fall off too and you'll know how to fix it for them (or even teach them) in a jiffy!
4. How to make a budget and stick to it.
5. How to tie a tie.
View this video on YouTube
OK, so: I'm 29 and I don't know how to tie a tie. I know it's bad, but that doesn't mean I shouldn't know how to do it. I'm fucked if I have to go to a wedding, but you don't have to be like me. If you don't know how to tie a tie, just watch this video and practice and you'll be a pro in no time.
6. How to negotiate:
7. How to pick the right running shoes, because exercise is important.

8. Which shoes go with which pants.

9. How to not pee on yourself when using a urinal.
'Nuff said.
10. And speaking of peeing, you should know how to clean the damn bathroom!

11. How to communicate your feelings.
12. How to give good and useful advice.
13. Own a sexy pair of underwear.
14. How to get a haircut you actually like.

15. Know the differences between wines.

16. Learn how to iron a shirt in 90 seconds.
View this video on YouTube
Iron your damn shirts. It makes them — and you — look so much better.
17. How to tip properly.

18. Stop caring about what other people think.
19. Make sure your pants fit!

20. Know the different types of screws and what they do.
