To get this achivement, just start a non-xbox-live game from the start lobby (where you can view your cars, trophies, number of fans, etc.) Have someone else play with you, and on the race selection screen select the race type and race course, and then on the start race screen select the icon with the steering wheel that has "2P" above it. NOTE: Do not select the steering wheel with the word "1P" above it. The person playing with you will just be spectating. If there is someone next to you and you select "2P", the screen will become split screen and you will get the achivement at the start of the race.