To raise the girl’s fondness on dates and make it a successful date you will need to take her places shes likes.
There are provided ratings of what each girl thinks of each place that range from 0-100, 100 being she loves it, 0 being shes hates it.
For the first time in the series, Grand Theft Auto IV features "morality choices" in several points of the game, in which the player is forced to choose between killing or sparing a character, or killing one of two characters.
Each girl is awake from different hours in the game’s day.
When you do so, have on a completely new outfit, pick her up in Roman's Taxi, and take her to eat.
When you get back, you'll have the option to say goodbye or ask if you can come up. She should say yes, and you get the achievement after a sweet little cutscene. If you go to the internet post-campaign and meet up with... Anyway, her real name is Carmen, and you just date her until she says yes to you on something like the third date.
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.