Spend time with your friends to build their opinion rating. Once this rating is high enough, they will be added to the contact list in your address book. Activities can then be planned with friends. Once their opinion rating increases enough, their distinct special ability is unlocked. To avoid a negative opinion rating, always accept invitations from your friends. If you really do not want to spend time with them, call them back immediately after accepting to cancel. They will not then be offended and give you a negative opinion rating. Also, remember your friends' sleep habits when calling. If you call when they are sleeping, this will affect your friendship as well.

Turn on subtitles if you have difficulty understanding some of your friends. This not only makes it easier to understand the accents of Jacob and Badman, but also translates the Serbian mutterings of Niko and Roman, and the Russian Mafia's native tongue.

• Roman: Free taxi rides, and assignment of taxi driver missions.
• Little Jacob: Inexpensive weapons 
• Brucie: Car theft missions, helicopter transport to select locations in Liberty City
• Dwayne: Provides gang members to help with missions. Remember this when making your decision about who to kill in "The Holland Play"
• Packie: Car bombs