If you played the original Stupid Zombies, and you enjoyed it, then you know exactly what to expect out of Stupid Zombies 2. It’s essentially the same game, just with different stages. Like the first one, you get a limited number of shots out of your rifle, and your goal is to kill all of the zombies on the screen using as few shots as possible, The zombies crawl and move around in this one, so it gets much more complicated, but that’s not necessarily a disadvantage.
For one thing, your best bet is to figure out the best angle at which to fire your shots, and then wait for the zombies to place themselves in the area that you want to shoot. After that, shoot them and watch them go down and watch yourself earn all of the stars. The less shots you use, the more stars you earn.
Also, go for the headshot whenever possible. Headshots offer double as many points as any other kind of shot in the game so even if you end up using all of your ammunition, you can still increase the amount of stars that you earn on a stage simply by hitting enough zombies in the head with a bullet, so make that your focus as much as possible.
Otherwise, much of the game is just dumb luck. If you only end up with one star on a stage, play that stage over and over and try to kill the zombies every time. Eventually, after playing the stage enough times, you will end up earning enough points, and using few enough shots, that you earn 3 stars on a stage instead of just one star on the stage. Playing a stage over and over is still the best way to earn points and to try to get three stars on each stage. The more stars that you get, the more stages that you will unlock.