Ok so I've only been playing for a little while, and so far have 4 stars. But my question is, what ways are there to get stars besides the "quest" ones? Like in Mario 64 you could get stars from the level quests, but also from collecting 100 coins. In the first galaxy, it seems kinda impossible to reach 100 coins, so what other ways can Mario get stars?

I like to cover my tracks from the beginning, so I don't have to go back if its not necessary.

Collect as many star bits as you can. Every now and then you'll find a hungry Luma that you can feed them to in order to get to another star.

Well, there's the find Luigi missions, but those are still sort of "Quests". Basically ALL of the stars are quest based... When you get to go back to the Gate to the Starry Sky from the beginning, if you collect 100 purple coins you get a star.

There are TONS of different missions though, so it very rarely seems like "Just another mission".