Press "Gas" just before the last number turns green during the pre-race countdown.

When the two lights turn yellow, press A on the last light.

On a track that is open at the start, such as Shy Guy Beach, hold [Left] or [Right] + "Brake" when Lakitu appears. Then, get a rocket start while still holding those buttons. If done correctly, you should whip around the player next to you and make a circle. When you want to go straight, stop turning. You will not slide. This is better than a normal rocket boost because you do not hit anybody while boosting. This works for all characters.

Just before a race when Lakoota is doing the lights, hit the gas which will make smoke appear. Keep the gas before the race just before the smoke comes out, there is a chance that you will get an automatic burst-start when the race begins.