Hi, I'm Thomyohne, these are some good hints / cheats for Mario Kart DS!!

~Unlock Mission 7~
Get at least a star-ranking on Missions 1-6 to unlock Mission 7!!

~Preform a Power-Slide Turbo Boost~
When driving hold "R," and while holding "R," hold the right and left arrown keys on the D-pad, and wait til the sparks turn red / orange, then let go.

~Get Blooper's Ink of the Screen~
When Blooper, the squid squirts ink in your face use a mushroom, to get it of your screen. WARNING: Power-slide Turbo Boost will not work.

~Getting good Items~
When playing Grand Prix, or VS, get in last place on purpose, and get a golden mushroom, lighting, a star, or a bullet bill. Get to first place, and use it to get a "boost." WARNING: Don't do at small places.

~Avoiding Boo~
When Boo comes to you, hold X, or R, and you will hold it behind you. Boo can't get it. WARNING: This won't work with bullet bills, blue shells, mushrooms, and stars.

~Tricks~
When playing Battle, hold a shell, or banana behind you, and get in the front of your opponent make it hit them.

~Make People Lose Balloons Faster~
Easy Ways, (Lose 2 Balloons)
1.Hit someone with a mushroom and knock them off the stage.

2.Hit someone with 2 shells.

Hard Ways, (Lose 3-4 Balloons)
1.Throw a throw a shell at someone, his them with a mushroom make them it a banana and fall off the stage,(Hard takes practice)

2.Hit someone with a mushroom, make them hit a banana, and make them fall off the stage.

~Shortcuts~
At Bowser Castle, while on the rolling circle, keep going and you'll see a thwomp, go that way.

At Mushrooom Bridge, after coming out the first tunnel, you need a mushroom, go through the sand part and fall.

At Banshee Boardwalk, When you enter the place with the bats, turn to the left to avoid the bats.

At Delfino Square, you will see to crates, go through the sand part with mud with a mushroom.

The Sky Garden has like 3 shortcuts, you need a mushroom to do them.

THAN