Techniques

(all techniques are for mx, untested for atv)

Wheelies are faster

Hold the down button down when travelling in a straight line. This will allow you to go faster but turn slower. Probably because you push more weight down into the motor wheel or something. May also be able to gain additional speed by touching the ground as soon as possible, by leaning back as far as possible when touching the ground

Height boosts at top of ramps

If you press the up button when leaving a ramp, you will gain a height boost. This is illustrated by the meter in the bottom right. Essential for some courses.

Clutch control

At speeds lower than approximately 40 km/h, you can gain speed much more quickly by pressing the clutch in for a couple of milliseconds. This allows the engine to get up to speed, and then when it is re-engaged, you will go shooting off at an acceleration much faster than if you had not used the clutch. Essential for hill climb, and useful in supercross.

Low speed quick turns

Holding down the up button while turning at speeds below 30 km/h will allow you to turn much more quickly. Won't work if you use the clutch.

Opponent boosts

Being hit from behind by an opponent will decrease their speed by 10 km/h and increase your speed by 10 km/h.