1. When talking to a girl, don't EVER make jokes about her weight or age. You'll only get her annoyed. No, wait, you'll get her really mad.
2. Self irony is also a delicate matter, so please, be careful when using it. Self pity is a dangerous strategy.
3. Don't get in conversations on topics you only have superficial knowledge of, you'll make a fool of yourselves.
4. If a girl is asking you to join her on a night out with her friends, she's not necessarily interested in you.
5. If you already have a girlfriend, don't bring her up every 5 minutes. Seriously.
6. Check your spelling every time, no one likes a grammar idiot.
7. Don't be clingy, it's probably the easiest way you can fail. Girls like bad boys (duh). I won't even comment on stalkers.
8. Don't send her idiotic (presumably funny) links or jokes. Also, songs older than 10 years are a total no-no.
9. Don't criticize her unless you can actually bring reasonable/non insulting arguments for it. Again, don't criticize what/where she eats.
10.You won't get her by mentioning your macho abilities. Or if you do, she's probably not worth the trouble.
11. Before going out, look yourselves in the mirror and lose anything that could also be worn by your grandpa. For god's sake, textile napkins are disgusting.
12. Don't exaggerate your showing off. Careful, there's a delicate balance there.
13. Don't even try to imply that she's smarter than you. Pity won't bring you sex or anything else (this only happens in crappy hollywood movies).
14. Calling her cheesy names or being over-polite will only remind her of her dad. Unless she has some oedipal complex, trust me, it won't work.
15. Don't invite yourselves over to her place. It's lame.
16. Using alcohol to make things easier is a good idea, as long as you don't get her too drunk. She will still remember you sucked, plus she will never forgive you for the terrible hangover.
17. Irony may be used, unless it's (again) related to her age or weight. I can't stress that enough.
18. Don't bring flowers on a first date. Laaaame. Pay her compliments, but make sure it sounds plausible. Sexual jokes are only allowed after she has already shown interest in you.
19. Nobody likes a mama's boy. Grow up!
20. Finally, if she's already said no, get over it. Please, show some self respect.