You get a lot of points, and therefore stars, by forming and solving series of 4s, 5s and T- or L-shapes. In this way, you can considerably improve your own star rating, so it can sometimes be more interesting to make more moves and prepare good combos than to finish the level as quickly as possible. To get a good rating and finish a level, stunts are also an advantage. Stunts are when one move solves a match and other chains are solved afterwards. Each level can be repeated to improve the level's score and thus the total score and stars. Have a nice day Sofia