After you retrieve the Star Piece from Moleville Mountain, you can go to Booster Pass to follow rumors of the Princess.
Reach the Tower
Beware of the Lakitu in this area that drops Spikeys on the ground.
You can optionally go northeast, then northwest to a dead end. If you stand on the plant, then jump, you will reveal a hidden chest. Go southeast from there, then southwest to where you first entered the area.
Go east and jump onto the ledge, then make your way northeast, but be careful not to jump onto the plants if you want to avoid a battle, because some of them are Artichokers in disguise. Before you go northeast to the next area, go to the north corner of the highest ledge and jump to reveal a hidden chest. (If it doesn't work, go slightly south from the corner, then jump again.) Then go northeast from there to the next area.
Go east, then northeast. Go northwest through the narrow gap, and jump northwest at the end to jump onto a hidden switch. This will close all of the holes that the Spikeys are hiding in, and you will get coins for each.
Go southeast out of the gap, then go northeast to find a Flower, which increases your FP by 1.
Then go southwest until you can go west, and jump onto one of low stone ledges, and keep jumping to reach the top of the area. Go northeast to exit the area. Then you can go northwest to Booster Tower.