At the beginning of a race, when do you hold A for the initial boost?

Solution 1:

There are 2 levels of boost. If you are driving a kart, you can tell which one you get by how many of your exhausts spit fire. If both spit fire, then you've got the maximum boost. If you are driving a bike, then your bike will do a wheelie when you get the maximum boost.

If you watch the numbers come on the screen it goes 3 - 2 - 1. The numbers kind of drop in from the top. You need to hit the button just as the number 2 gets to the bottom of it's downwards animation. It takes a bit of practice but after a while it becomes second nature.

Another tip is to count it down in your head - then you get the timing just right naturally!