World 1-1

Coin 1 (after checkpoint)

Just after the checkpoint, you'll find the first coin hovering above a trio of item boxes. To grab it, grab the Propeller Suit from the item box below (or the one just beyond) and use it to spin into the coin. If playing multiplayer, you can also jump off a teammate's head.

Coin 2 (after checkpoint)

After the checkpoint, stop at the third spinning-ground section (also the 5th one in the level) and wait for an opening to reveal itself, allowing access to a warp pipe (you may have to wait a while). Inside, you'll find the second coin between the two pipes--wall-jump or propeller into it.

Coin 3 (after checkpoint)

You'll find the third coin just above a signpost on the higher route, after the red coin ring (also above the main course). Keep in mind that if you've taken the lower route that the coin may be too high to see--it's just before a trio of goombas. It can either be leapt to from the nearby platform or propeller hat'd into.