First room: Easy enough. Go right.
Next room: Go through the door there to get some eggs (beat the Boos inside for a flower--ricochet eggs off of walls to hit them with your back turned), and use an egg to hit the ? cloud. Follow the arrows to the red switch, stomp it, and get the key from the ? cloud over in the corner. Head over to the left and go through the locked door near the yellow platform.
Next room: Go up to the top and down the pipe. You're back in the previous room, except the stairs you made with the first ? cloud are now gone. Ride the yellow platform to the middle ring and go right. Go through the pipe at the end.
In the next room, pass the fire bars and ride the log over the lava (it's safe) to the pipe. Enter. Go through the door at the end of the next room.
Don't be afraid of the odd platforms ahead--if you land on brown, you'll be safe. The red door to Bigger Boo is at the top. To beat him, bounce eggs off of walls at him five times.
