Instructions
Get all the mission-based stars in the game. These stars are retrieved by going to a galaxy and receiving a visual clue about the star. After this, you progress through the galaxy until you find a star. Once all the blank star slots for a galaxy have been filled in, you have found all of the mission-based stars in that galaxy.
Get all of the comet-based stars in the game. For every galaxy with three mission-based stars, you will have the opportunity to get two extra comet-based stars. These stars will usually require you to get a mission-based star, but with an extra challenge involved.
Get the game's secret stars. For every level with three mission-based stars, there is one secret star. You can get clues for some of these stars from Luigi's letters. Otherwise, you will have to search the level to find the star.
Get the game's three green stars. These are found in "Battlerock Galaxy," "Dusty Dune Galaxy" and "Buoy Base Galaxy." These three stars will open up the three trial galaxies, from which you can receive another three stars.
Get the game's Observatory Stars. These are found by feeding all the Hungry Lumas in the observatory. Each time you feed one the right amount of star bits, it will create a galaxy that you can get one star from.