This mission will begin at Michael's house and you can switch to him to start it if you want. After a little friendly reunion with a past friend, head outside and get into the car. Head to Maze Bank Arena and when you get there, head inside. A cutscene will play out, which will bring you to a chase with Lazlow.
Chase him on foot out of the building, then grab the big rig truck and follow Lazlow in his vehicle. Note that you can't really catch up to him, so just keep close enough so you don't fail the mission. Also, you can detach the trailer if you want, but you need it on to get 100% completion on the mission. The truck is pretty tough on handling turns, so make sure you don't go too fast on them.
There will be one point where Lazlow will go on some train tracks, but stick to the road. Eventually, he will jump off into the Los Santos River, so follow him. As you pass the first turn, you'll see that Lazlow has stopped. Watch the scene that unfolds, which will bring you to the end of the mission.
