Here are a few:
Make sure you're snaking so frequently that the sound effect for the first mini-turbo doesn't get a chance to stop if you want to hold your own against pro-players.
At the top of a hill, if you mini-turbo and leap (yes leap) off of it within half-a-second, you'll keep the mini-turbo speed longer. (If you do this over the three-hill combo at the end of CM, you can get over all of them on one mini-turbo without slowing down at all!)
Keep mushrooms for shortcuts, even if you see a spiny coming (you can dodge them by mini-turboing and hook-hopping at the same time.)
I failed to do it, but there's a shortcut that takes out a quarter-of-a-lap if you have a mushroom and are doing the spiny-dodge skill (without a spiny of course) there.
Also, you can destroy Yoshi Circuit and Desert Hills by PRB'ing there. (I've once PRB'd a whole lap on DH. It's pretty much a shortcut blitz)