From the Super Mario Wiki
Moguls is a real-life based event in Mario & Sonic at the Olympic Winter Games. It appears in both the Wii and Nintendo DS versions. The player must ski down a bumpy slope and collect the green arrows to get points. Doing tricks off the jumps increases the total points in the performance. There are a total of twenty-two arrows (thirty in the DS version). It is a variation of Freestyle Skiing.
Start – Tilt Wii Remote and Nunchuk down
Turn: execution of moguls – Tilt Wii Remote and Nunchuk to the side
Start – Hold stylus on "2" and flick down on "GO!"
Turn: execution of moguls – Rub the Touch Screen
Tricks – Slide stylus in different directions