Downhill snowboard

Use the jump button at spots where the ground angles down, often you can get enough air to do a flip on pretty level ground.
Use your momentum no matter which way it's spinning.
To speed up your flip, do a grab, so to slow down your spin after several flips, release your grab.
Often try to jump and do a flip about 3-6inches (of screen space) before a cliff/jump because that way you can do a double or triple instead of one less.

unlock the second character and snowboard (by getting 8000 points) before playing any other level