Easy experience points
Leave your hideout near the river and train tracks and run west to the nearby highway. Raise your ctOS wanted level by killing civilians while they are still in their vehicles so the police will not appear yet. Move north along the highway continuing to kill people inside vehicles until your wanted level is full then get to the L-train station to the west. Jump over the fence, steal a vehicle, and allow yourself to get caught by the yellow police scan. Drive the car through the wooden fence just to the north of the station then drive into the train tunnel and stay on the left side tracks. Wait in the tunnel for an oncoming train. The train will not hit your vehicle. Begin driving backwards to allow the train to enter the tunnel. After it is inside the tunnel, exit the vehicle to block the tunnel. Run ahead and enter the train. Make your way to the end of the train. The scan should be white and less than 10 percent at this point. Let it run out to get 300 experience points for escaping the police. Wait for the helicopter to leave the mini-map, then shoot the ground with your gun to trigger the white scan level again. Wait for the scan to run out, shoot the ground again, and repeat the process for 300 experience points each time. If your cTOS level decreases, kill another civilian on the train to raise it. Return to your hideout and sleep to save your progress at regular intervals.