I change this around a little over time, but I have a rigidly-consistent rule that on every iOS device, the Settings app is the top left item in a folder that is in the top left corner of the home screen. And then on the phone, the things to which I need fastest access (or one-handed access) gravitate to the bottom right. The wallpaper is the battlestar Galactica in low light, which passes the Grey test of being aesthetically-pleasing and providing clean separation between apps.
