According to the instructions you need to wait for the ring to turn red, but it's constantly red so I guess part of it is a stroke of luck? According to threads though, it's getting the cross hairs (the four lines outside of the ring) to be in the dead centre which itself is difficult and effort. I've noticed it's significantly easier to achieve flawless on the first trip which gets harder as the game progresses. Awesome is indeed the rarest score to achieve (I've got it four times though ya'll mad) but flawless is the best I think?
EDIT- As someone mentioned, the quicker you snap them the more likely you will get a Flawless. This worked for the later rounds which was much harder, but explains why it gets harder to get Flawless as often. It's best to snap them as soon as they appear, which can be difficult and requires practice in combination with dodging the obstacles.