The story focuses on Johnny Klebitz, the vice president of the Lost Brotherhood motorcycle gang.
He has been the gang's unofficial leader ever since the president, Billy Grey, was put in court-mandated drug rehabilitation, and has forged a truce with their arch-rival, the Angels of Death.
From there, you can try to contact various women and hope that they respond to your advances.
The status of various inquiries can be found by checking your e-mail at a later date, where you'll either get a counter-inquiry or a downright rejection.
There are two females in the game you must date—Mallorie's 'friend' Michelle and the O'Reary boys' sister Kate—but other than that, dating is completely optional.
However, that shouldn't daunt you from building as many relationships as you can, because they happen to provide some of the deeper and more rewarding experiences Grand Theft Auto IV has to offer.
The game begins with Billy being released from rehab, resuming his leadership position and creating tension with Johnny by trying to resume the war with the Angels of Death.
Since Johnny is an experienced biker, he can actually stay on his bike (and survive crashes) at speeds faster than walking (something Niko in GTA IV is notoriously bad at), although his corresponding dislike of cars means his four-wheel skills aren't as fancy as Niko's.
This is all about personal feel and how much the girl likes you.
There are no absolutes, but it should go without saying that trying to get with a girl after your first or second date is likely to backfire, while she might be confused if you're not asking to come upstairs after, say, your fifth or sixth date. Then, when the girl really likes you, going upstairs for some coffee is a given. That should be the first question you ask yourself when you and your female friend part ways.