Kinect Joy Ride

Hey everyone I have found a very easy way to get both flawless achievements. Ok so start up a trick event with one or two people which ever achievement your going for, im not sure if they stack but they only take about 1 min to do each one. Ok so make sure your xbox controller is near by, and start the event. Now make sure you or both of you get a Flawless on the very first trick, then quicky press the xbox guide button. The game should have paused, now select back to main menu and pop theres your achievements!

Everything Perpalicious wrote is good and helpful, but here is the key to getting this one easy:

Play with someone who is bad at Tricks.
Under the normal time limits you will have to do about 11 Flawless tricks, play with someone bad and you'll only have to do 1/2 the tricks for the achievement. I played with my 3 year old and only had to hold 5 Flawless to unlock this achievment.