Don't take your friend to an activity that he doesn't like or your 'like stat' will reduce.
You can perform upto four activities on each outing in order to give your 'like stat' the highest possible boost.
It's best to wait until you have completed the main storyline before taking on the girls from the internet, since the more girlfriends you have, the more attention they require and the more often they will call.
Call your friend and perform activities with him on a regular basis to increase your 'like stat'.
This stat (amongst other friend stats) can be accessed from the pause menu under the 'Stats' section.
Each friend offers a 'special ability' in return for maintaining a good friendship.
In order to unlock a friend's special ability, you must have a high 'like stat' for that friend, and this stat is based on how regularly you hang out with your friend.
Friends and girlfriends become available as you progress through the storyline.
There are five friends and five girlfriends in total, and each character has a unique set of preferences.
Don't call her too frequently or her respect for you will drop.
You can date as many girls as you like, but the more you take on the harder it becomes.
When her opinion of a specific place falls below 25, she refuses to go there anymore.
In order to get the maximum success out of a date, therefore, you should refer to the initial opinions of all the activities listed in the table below, and try to vary the activities from date-to-date.
Nico can set up dates with three different women through the internet in addition to the two that he meets in the course of the storyline.