Koopa Troopa Beach - When approaching a part of the map go left and a ramp leading up to a cave will be there. Use a mushroom to blast up it and into the tunnel.
Dk's Jungle Parkway - You can advance the lap counter a lap without
going around the track in DK Jungle Parkway. Try to jump into the wall
to the left of the exit from the tunnel just before the Starting Line.Your
angle of approach is important. If you angle too far to the left, you will
fall back into the tunnel. If you angle too far to the right, the trick
won't work. You want to fall into the "dark
space" behind the wall. Lakitu will pick you up. If he puts you back
on the track, inside the tunnel, the trick worked.
Mario Raceway - To take this shortcut, you will need a Mushroom.The point where you will need to jump to get over the wall is just before the fourth turn (the hairpin turn around the giant mushroom). After the third turn, veer slightly to the left, and go slightly up the hill on the left. Turn sharply back towards the wall and hit your Mushroom boost just before you leave the road, jumping at the same time. You'll want to aim just to the right of where the sections of wall intersect. If you make the jump, you will come down near the giant green pipe.
Yoshi Valley - After you go through the maze, you'll enter
a long, curving road that leads towards the giant egg. You'll see a fence
on the right hand side of the road that leads to the left turn loop. Head
for the end of that fence, and a little before you go over the edge, turn
sharply to the left.
Just before you leave the track, jump! If you timed it right, you will
make it across the valley to the lower track on the other side.
Rainbow Road - After the Starting Line, the track goes a short distance and then descends down a monster hill. Near the top of this hill, on about the third yellow stripe, hang a hard left turn and go over the fence. If you angled your jump correctly, and had the right speed, you will land on the track below.
Kalmari Desert - To do the shortcut, you will need a Super Star. From the second crossing, turn left and follow the tracks to the entrance to the train tunnel. Activate the Super Star just before you enter the tunnel, and your lap counter will advance by one around the min-point of the tunnel.
Wario Stadium - It's possible to jump over the wall to the left of the Starting Line using any one of the four small jumps there. Approach the wall at high speed so that you are driving directly at it as you reach the peak of the small hill. Jump just before you hit the wall and you'll sail over.