Mario Kart 8 Wii U Cheats

General Tips

Always be drifting. If you want to know what separates the good players from those who occasionally do well, it's drifting. If you drift long enough you get a speed boost (indicated by a blue spark and then an orange spark for bigger boosts). Thus, it's important to drift early around corners.
If you perform a trick before landing from a great height you get a little speed boost.
At the start of the race, hold the accelerate button just as the number two appears on the countdown to get a speed boost. Don't do it too early though, or you'll blow out your engine and be at a disadvantage.
Don't be afraid to play Mario Bumper Kart in key situations and ram opponents into hazards/off the course.
If you stay behind a racer for a set amount of time you get a speed boost. This is known as drafting. Just be wary of banana peels!
While gliding, pulling back on the stick allows you to go higher. You may even find some secret areas...
Bump into other racers in anti-gravity sections to get a speed boost.
Hold items behind your kart for protection, especially if you're in first place.
Skilled players can try a new technique called fire hopping, in which you continuously hop to extend a boost. It can help shave off seconds in Time Trials and gives a slight advantage in competitive races.

Guides

Unlockables

Miiverse Stickers

You'll begin with 28 out of 90 stickers available. Finishing Grand Prix mode with unique characters unlocks an additional 30 stickers, one for each character. The final 32 stickers are available when you defeat the various Time Trials staff ghosts.

Golden Vehicle Parts

You can unlock gold vehicle parts by satisfying the corresponding requirements, as indicated below.

Gold Standard (Kart) - Earn a rating of at least one star on every regular Grand Prix (150cc) and Mirror Mode race.
Gold Tires - Beat every staff ghost in Time Trials.
Gold Glider - Collect 10,000 coins
Gold Handle - Use the Wii Handle for 50% of your most recent 100 stages.

Extra Cups

In addition to the Mushroom and Shell cups that are available as you begin the game, you can access the tracks indicated below by placing first in the corresponding circuit, as indicated below.

Flower Cup - Clear the Mushroom Cup
Star Cup - Clear the Flower Cup
Special Cup - Clear the Star Cup
Banana Cup - Clear the Shell Cup
Leaf Cup - Clear the Banana Cup
Lightning Cup - Clear the Leaf Cup

Extra Racers

You unlock additional characters at random, as you complete the various cups with a gold medal. There are a total of 14 characters that can be unlocked in this manner. Playing through the same cups a few times won't unlock additional characters, so make sure you earn the gold on each cup in the 50cc and 100cc classes if you want them all. Below is a list of the characters.