Sidestepping

Sidestepping is the fastest method of ground movement in the game.

To perform it, simply boost and then start holding LB or RB.

You can release boost after you start sidestepping, and that won't make you lose any speed, but it will affect how you turn.
Holding boost will allow you to do a sharp turn on each sidestep, while releasing boost will make turns more gradual.

Note that if you stop being on the ground and try to keep sidestepping, you will air dodge instead, which is really slow.
This is most common on Chaos Island, where there are many small pebbles and other objects that can easily put you in the air.