If possible, use a bluetooth controller instead of just tilting your phone. This will make you more precise and give you more control over the vehicle.

The oceanic environment is the hardest to maneuver in. You will need to spend time doing a number of races there to get the real feel of it. Don't forget about the waves.

Use your skill points to upgrade the start boost, drifting and get a boost bonus. After you've acquired those upgrades, you can spend the rest of the skill points on new tricks.

Do the tracks multiple times to figure out all the shortcuts and get the best time.

You can also do tricks on big waves, and not just regular jumps.