I've found a way to get a hole shot almost 100% of the time. You just have to get the timing right. This will make it very easy to get them as long as your bike is reasonably fast. It will be reasonably fast, since the game requires you to use a certain class of vehicles for a given race. You'll exit the gate first with my technique. Make sure you also cross the 1st turn, indicated by a white line or object (Credits to MxSvnty4).
I found this new technique from trying to follow a comment.
Credit goes to jamesevans23 who said: "Great Solution, just to add I found that when the computer opponents starting revving their engines the gate was going to drop very soon, meaning that you could let go of the brake about a second after they started doing that."
The technique:
I experimented with the timing a little bit and found something that works well. Once you hear the engines of the other racers revving,: Immediately or after a half to a full second, hold the clutch
, the gas
, and forward on the left analog stick
(Credits to MxSvnty4). When I did this, as long as I got the timing correct, I launched out of the gate in 1st place. Make sure to release the clutch when the gate begins to drop. This technique works very well.