When the level starts, move left to find the first Star Coin floating above a hidden platform.
The second Star Coin is located in a hidden area. Hop onto the Block at Point 2, then jump straight up to find an Invisible Block containing a Beanstalk.
Climb to the top of the Beanstalk, then hop across the spinning Blocks to the right. Jump up and grab the Star Coin, then drop out of the area.
When you pass through the Red Ring at Point 3, the red coins appear above the nearby platforms. Ride each platform to collect all of the red coins before they vanish.
The third Star Coin is floating between the platforms at Point 4. Slip through the gap between the circling enemies, slide down along the side of the platform, then wall jump out of the gap before the next enemy passes above you.