How to get the best speed start from the starting line
To get the best boost possible from the start line, hit the accelerator the moment you hear the 'beep' sound for the two counter. It takes a bit of practice to get used to, but you'll soon be nailing those perfect starts.
How to drift for boost
Drift around as many corners as much you can, but not to the detriment of the next turn. In order to gain those mini-boosts while drifting, quickly toggle the left stick or D-pad left and right. If you hold the drift long enough the flames on your rear wheels will switch to red, giving a longer boost.
How to boost speed by collecting coins
Try and collect 10 coins within the first lap. The more coins you have, the faster your kart goes. If you get hit by an item or obstacle on the track, you'll lose a few coins, so try to pick some up as quickly as possible. Equally, if you hit another racer ahead of you with an item, they'll drop coins which you can pick up as you fly past.
How to make the most of your items
Although Nintendo has removed the ability to double up on items, that doesn't mean there aren't still little tricks you can use to make them even more effective.
With shells and bananas, for instance, holding the 'ZL' button instead of using them straight away will put them behind your kart, acting as a great defensive tool until you decide they're best to use. Just know that when you turn around corners, the items won't protect the side of your kart.
If you get a cluster of three offensive items, like three red shells, don't waste them all on the first racer ahead of you by throwing them all at once. After you've thrown the first one, if it hits, try and move up a place before throwing the next, as then it'll target the next racer.
You can choose to throw items in front or behind by pressing up or down, too, but items with lock-on capabilities won't do so if thrown behind.
Take the shortest route
Sometimes tracks will place floor boosters on the outer part of the track, making it seem like you gain an advantage by taking the longer route. But if you drift along the apex of a turn, you'll negate the benefit of the boosters and still be ahead of any driver who tried the alternate road.
Look for shortcuts
Shortcuts are great for getting back into a race. Some will require you to have a mushroom to cut across the grass to exploit them, but others will be simple little jumps that, with a bit of practice, are well worth taking.
Toad's Turnpike is a great example, with its anti-gravity sections on the walls either side of the road, which are great for avoiding the congested traffic which can knock you back, costing coins and time.
How to dodge items
It can be possible to dodge targeted items like red shells without having any items yourself. If you get a warning of an approaching item, take turns around corners as close to the apex as possible, use any jumps that you can see, and swerve around any NPCs on the track. Hopefully the item crashes into something in the terrain, leaving you free to carry on racing.