This achievement can of course be unlocked regularly but I would recommend boosting this achievement with 3 other players. This way you can make sure that everyone will get his/her achievement in just 4 races.
Firstly, you have to start a land race. You can either do this at any race point in the city or you can just host/join one. The map does not really matter (they just vary in length and difficulty) but I would recommend the map "criminal records" because it's basically just a circle you have to drive.
After that make sure that you select "rally" race in the menu because this is the game mode this achievement will be unlocked in. Also you can choose between a driver/ co-driver preference. The person who wants to go for this achievement should choose co-driver (especially if you try this in a regular session).
The co-driver then has to navigate the driver through the checkpoints, since the driver has no clue where to go to in these races. So (and i can't stress this enough) communication is key. Always use a headset or if you do not have one use the kinect mic. to talk to your driver otherwise you will not have a possibility to navigate your driver.
After you have navigated your driver through the race the achievement will unlock for you and you can swap roles.
You have to finish 1st. in these races to unlock the achievement AND you have to race against another team. It is possible to start these races with just 2 people but you won't unlock the achievement afterwards (This is the same for the "numero uno" achievement. The race will not count as a win if not raced against another team).
Hope this helps you guys ;-)
Any improvements? Please let me know in the comments.