Most books on Responsive Web Design (RWD) say the same set of things. I’m willing to bet there’s more to the story than these books are letting on.

1. Use relative measurements in CSS, percentages and ems. EMs are relative. they’re based on a simple equation target size ÷ base size = relative size
2. Declare images to be 100% of the div their contained in.
3. Establish media queries to change things at different screen sizes
4. Save bitmap images to be sensitive to retina display (for my money that’s 326 ppi)
5. Use JavaScript solutions sparingly
6. Minify your code
7. Remember that the iPhone isn’t your only viewport