Checking Out - win a game of darts in the quickest way possible (6 dart checkout
Jesus. Is this just straight Bullseyes?
Every Race - win every type of race mode at least once
Not sure if this can be considered a tip, but there's only 3 race modes, right? Standard, GTA, and Rally? So just do all three for Land & Sea and you'll be solid I think.
Thanks to Xerofox for the rambunctiously romantic signature!