Kill the ghost to the left of the fountain in the backyard and dive into the little cage.
Go into the mansion and kill those little ghosts. After Mario killed a certain number of little ghosts, the Big Boo appears in the entrance of the mansion. Kill it and Mario will get his first star in this stage. Pound to kill them.
Kill those little ghosts in the Merry-go-round under the mansion. When the Big Boo appear, kill it to get a star.
Go through the second door from the left on the first floor, and Mario will see 3 books floating in front of the bookshelf. Hit them in sequence and Mario will find a star in the door behind the bookshelf.
Collect 8 red coins.
Behind the piano in the first door from the left on ground floor.
2 of them are on the top of two bookshelves in the second door from the left on the ground floor.
In the first door from the right on the ground floor, moonlight through the window is shinning on it.
In the third door from the left on first floor.
Through the fourth door from the left on first floor. 2 red coins are hidden under two of the six coffins.
The fifth door from the left on first floor. Moonlight is shinning on it.
The star is just outside the first door from the left on the first floor.
Go through the fifth door from the left on first floor. Mario will find a bookshelf. It is facing a wooden platform. Look up and Mario will see there is a door on an extended platform. Get there by performing wall-jump. Then Mario will reach the penthouse. In the penthouse, go through a double door to the balcony. Defeat the Big Boo and get the star.
Hit the blue ! box, get the vanish cap and turn Mario into transparent. Then go to the penthouse as in star 5 as quickly as possible. If you are fast enough, Mario is still transparent when he reach there. Then go through a picture of a shy ghost and defeat a big eyeball by running around it to get the last star.