1. Round corners look better than sharp corners, round all corners
2. Background that are semi transparent looks better than opaque background, regardless how little the transparency is
3. Gradient, high light, shadow look good, add them to everything
4. Big text > small text, non-color (black, white, gray only) text > color text
5. Colorful icon = good, big and colorful icon = better
6. When in doubt, see Iphone