Friendships in GTA IV

After you do so many missions for someone, eventually they will become your friend, whom you can undergo specific activities with, including bowling, going to the strip club, and going for a beer. From that point onward, you can either call them with your phone or send emails to hang out. Hanging out with your friends is a fun way to work on your relationships with them so that eventually you can get their "friend benefit". Niko can also increase his friendships through certain storyline missions.

Activities

Get a bite to eat at any Burger Shot or Cluckin' Bell throughout Liberty City.
Get sloshed and ready to call a cab in the bars in Hove Beach (Broker), Steinway (Dukes), Purgatory (Algonquin), or Hatton Gardens (Algonquin). Being seen driving drunk will get you wanted stars.
Drive to one of the Bowling Lanes in Purgatory (Algonquin) or Firefly Island (Broker) to go Bowling.
Seek out the Pool Hall in Schottler (Broker) and play some Pool.
Throw some Darts at the Irish/German Pub in Steinway (Dukes) or the one in Purgatory (Algonquin).
Find one of the Strip Clubs in Northern Gardens (Bohan) or Tudor (Alderney) to catch some lap dances.
Visit the Cabaret Club in Hove Beach (Broker), the Club in North Holland (Algonquin) or the Comedy Club in Star Junction (Algonquin).

Benefits

Note: Sometimes your friend will NOT be able to perform their service for you. Due to excessive use or blocked during missions

Little Jacob - Drives to a location near you with a trunk full of guns to purchase at a discount (60% off). You can do this during a mission.
Roman Bellic- Sends a cab to pick you up and take you anywhere for free.
Brucie Kibbutz - Picks you up with his helicopter and takes you wherever you want. Due to the landing procedure, he only picks you up, drops you off at pre-designated locations (usually on a roof top), so you may have to land at a distance from your actual target and then walk the rest of the way there.
Dwayne Forge - Sends a car with two armed men who will follow and help you in combat.
Packie - Supplies you with a car bomb which can be place under any car and detonated with your phone.