Three of which are contacted via in-game websites, the other two through playing storyline missions.
Niko meets his first girlfriend, Michelle, during the mission Three's a Crowd.
Bloody clothes, hurting/killing innocent people - none of this will make your girlfriend any happier. You can do this by simply finding her in your phone, clicking her name and choosing 'Dump girlfriend'.
To meet one of the girls, press Contact Me on the bottom of her respective page, and she will send you an e-mail some time during the following days.
If it says she's interested, upon reading the mail you'll get an update in your Organizer, featuring the time and date of your appointment.
As long as her 'Like' percentage is above 60%, you can keep using this special ability.
If it drops below 60%, you won't be able to use it until you've had sex with her again.
You can only use their special abilities up to three times between two dates.