Getting the most out of my camera

Hey, I'm pretty new to my G4, and I was wondering how to get the most out of my camera.

I haven't downloaded any camera apps or anything, and just use the stock one. For pictures I take, I just leave the settings on auto, seeing as I don't know a whole lot about photography. How could I tweak the custom settings to work better under different circumstances and just get a better picture in general?