From StrategyWiki, the free strategy guide and walkthrough wiki

Desert Hills is the only racing track to introduce pokeys, a tall enemy with many "mini-pokeys" stacked upon each other to create one giant pokey. It's important to note that this track's soil is much thicker than that of other tracks, and going offroad into the soil without a mushroom or star will give an easy chance to your opponents to cruise by and leave you stuck in the dust. As long as you stay out of the dirt, avoid pokeys, and power boost efficiently, Desert Hills should be an easy track for any novice with a potent learning curve.

[edit] Tips

1. Snake two gestures on the straightaway right after the finish line. Only do this if you're confident that you won't screw up or get bumped, otherwise you may end up in the dirt off the track.
2. Power boost through the next two turns.
3. On the bumpy bit, where there are sharp turns, if you have a mushroom you can boost straight over the bumps and save a couple of seconds.