Super Mario Galaxy 2/Spin-Dig Galaxy

Star 1: Digga-Leg's Planet
In area one, get the Spin Drill power up and drill onto the tall area from the other side of the planet. The Luma there will turn into a Launch Star to send you to area two.

In area two, get the Spin Drill and shake the remote while on top of the square shaped raised part of the planet. You will appear on the other side on a tower. From there, walk to the right side of the tower and shake the remote. You will appear on the tall tower on the other side of the planet. Use the Launch Star and fly to area three.

In area three, jump across the disappearing platforms onto an O shaped area. Follow the path to the right and cross another set of disappearing platforms to find another Luma. Use the Launch Star to fly to the fourth area.

Get the Spin Drill power up and shake the remote. You will go inside of the planet where there are many coins. Shake the remote when inside of the small hole to jump out of the other side. Use the Launch Star to fly to the toad ship.

Area five is the area where you fight the boss.

Boss: Digga-Leg. To damage Digga-Leg, drill into it when his glass cage is facing down. Do this three times to obtain the Power Star.

Items
The Spin Drill item can be found all over this galaxy. In area one you will see a green 1-Up mushroom in a cage. Drill into the cage from the opposite side of the planet to get into the cage and obtain the mushroom. In the second area, The Comet Medal can be found next to one of the rock towers. In the third area, there is a 1-Up mushroom on the path to the right. Jump on top of the disappearing platforms to get it.

Star 3 (Prankster Comet): Digga-Leg's Daredevil Run
This mission requires you to complete the boss battle from Digga-Leg's Planet with only one point of health. Avoid all of the yellow drill enemies, but most of all, don't get hit.