From the start run right to draw the Big Boo out then double back to the start to grab Green Star #1 . Ahead you can snag a Fire Flower by leaping from atop the ? Block , it’s very useful for disrupting Boos. Take the top path and ride the couch up to a 1-Up Mushroom and Green Star #2 .
Exit through the door and avoid the Goal Pole, it’s fake and will just draw a bunch of Big Boos to you. Instead enter the next door, then ride the couch up and over a lot of Big Boos. As you move left you’ll find three 1-Up Mushrooms but only one is real. Green Star #3 is at the end of the path, just grab it quickly and exit.
Dash to the end of this area to the Goal Pole, but this one is fake too! Head to the bottom-left of this platform to find Cloud Platforms that lead to a Warp Box and the real Goal Pole.