During your playthrough, you will sometimes notice your mini-map quickly flash white followed by a flashing red/blue blip. This notifies you that there is a Random Event at that blip. These events range from catching a thief; to gang shootouts and giving a stranger a lift back home. For this achievement, you will need to be playing as Trevor and wait until you encounter a hitchhiker or drunk pedestrian who needs a ride home.
After the story mission, "Friends Reunited," you will arrive in Los Santos and already be playing as Trevor. Around the block from Floyd's safehouse, you will encounter a drunk couple who needs a ride home. You should use this time to get the achievement.
When you pick up the stranger, you will receive a popup notification on your the top left corner of your screen informing you that Trevor can bring them to the Altruist Camp in Chiliad Mountain State Wilderness (Northern Blaine County). A white “A” icon will appear on your map immediately. If you set a waypoint to the Altruist Camp, you can follow the new purple route instead of the yellow route that directs you to their house. Once you arrive at the Camp, Trevor escorts them to the front gate where the cannibals take them off your hands. At this point, you will unlock the achievement.