On Mario Kart (my mom's favorite game), there is a shortcut on Maple Treeway.  On the right, near the beginning, you will see a hole.  Go in.  It will slow you down and will drop you to 6th place.  But take it because the power block will give you a good power and then you will get to first place.

My favorite levels are Rainbow Road, Mario Circuit, and Luigi Circuit.  I like to be my own mii and ride the bullet car (your mii has to be short like a kid to use the bullet).