Ideally, what Jimbo said is completely false. But here in reality, a lot of times Jimbo is correct.
First off, Girlfriends require: a) Time, b) Money. You will almost be guaranteed to be without either of those two unless a) you are rich, b) parents are rich and spoil you with cash, c) you have a time machine.
You will meet many Freelance Indirect Prostitutes (aka gold diggers). These are the women who will make judgement on what trendy style of clothing exists, what car you drive, where you eat, etc. You get sex, they get money (indirectly through material goods). Ideally these women would be rounded up and shot (as well as the men), but what can you do?
Here's what you CAN do: smile a lot (have a GOOD smile, no missing teeth or yellow deformed teeth allowed), be funny (you cannot gauge your own funniness, but you have to be funny), as said before: have a good body (that's evolutionary, women dig cut guys -- talkin a swimmer/diver cut, not bulk, a healthy look), be present around her and hypnotyse her with your charm... then take the lead and ask her out (in a day of being PC, women still don't ask out men). Also, if you are chasing one, be VERY polite -- read a manners book if you must, but do that.
this is what happens with some of couples I knew:
1) male initiates "deeper" contact
2) male spends all money
3) male spends all time to fill some need of the female
4) female uses poontang to make male her slave
5) female dominates male in every aspect of life and uses him
6) end of relationship