Online play is virtually dead for this game so you will more than likely need a boosting partner. Once you have found a partner set up a ranked Knock-out match to 5 points, any track you like. If you are going for the Globetrotter achievement I would advise to do three different tracks for this achievement.
Quickest way is for one person to put their controller down while the other races away to get the point. Repeat 5 times in one race.
Rinse and repeat twice to get the Achievement.