It really goes without saying, but corner boost whenever you can. The corner boost is perfect for the twistier, narrower courses like DK Pass. However, some chicanes - such as the final twisty bit of road leading up from the beach to the finish line on Cheep Cheep Beach - are better navigated by finding the straightest line through.
This is where the lower screen comes in useful. Getting a speed boost from slipstreaming can be a game-winning clincher, but it's fraught with danger. Use the lower screen to see if an opponent is slipstreaming behind you, and if you're holding a banana, green shell or fake item box, now's the time to use it.
The risk/reward mechanic
It's worth hanging on to certain valuable power-ups, such as the blue shell, in order to use them at the best possible moment. However, be aware that you'll drop what you're carrying if you're hit by lightning or if another player uses a star. As such, you should always keep an eye on the player roster at the top left of the screen so you know what your opponents have got.
Snaking - the devil's work!
Snaking is generally a practice reserved for heels, blackguards and the very desperate indeed. It is, in short, frowned upon in polite company. Never do it while playing Friends online, and only in local area WiFi matches with everyone's consent. For those Worldwide and Continental online matches, though, everyone is fair game. That being said, here's how to snake...
Snaking is essentially corner boosting all the time, especially on wide straights. Play Figure 8 Circuit online enough times and you'll see people zig-zagging across the track and disappearing into the distance. This, friends, is snaking.
The trick is to get into a powerslide while heading as straight down the track as possible. It's really tricky and you'll need to be quick of finger, especially as you have to pull off a corner boost as quickly as possible.
Here's the tricky bit. After you've pulled off a boost, you need to push in the opposite direction on the D-pad and hit R at exactly the same time to go into a new slide.
Keep boosting and doing this and you should zig-zag across the track in a fairly straight line. It's a tricky thing to master, though. A tricky thing indeed.