The first Star Coin is on a Donut Block at Point 1. Stand on the Donut Block to the left and wait for it to give way. As you fall, hop over to the Star Coin and jump to the platform above you.
The second Star Coin is on a Donut Block at Point 2. Pass below the Star Coin and jump to the moving platforms. Jump up along the platforms as they drop down from the ceiling, then leap over and collect the Star Coin.
The third Star Coin is surrounded by Blocks. Trigger the nearby POW Block to quickly destroy the Blocks, then grab the Star Coin.
The ! Pipe at Point 4 contains a Mega Mushroom. Collect this power-up to smash a path through the rest of the area.