The biggest challenge of responsive design is decision making.
What are you trying to accomplish (publishing, commerce, marketing)? The content determines the design.
How does this responsive site exist with other products on the same devices? Is it replicated or differentiated from a native application? How does it adaptively serve up images based on the view? What is the technology (CMS?)? What is the content, and what is needed on what device? For functionality, where can value be added? It can almost be more app-like. It isn’t page design it is interactive design.
How you prioritize is a big challenge. Think big (full page templates) but also be thinking about the micro elements (icons buttons). I isn’t mobile first, it is ALL platforms at once (more, but simple). Where to you place your breakpoints or midpoints?
How is the site used? Using the system is as important as the system itself. You need to look at everything (org structure, resources, CMS access, etc.). Best practices: team composition, argue early and often, prototype early and often, tools.
The Times of London
The reading experience has changed. Even the web isn’t a great experience, but then the iPad showed up so The Times developed a way to read it there. Then Android tablets showed up and made it more complex (sizes resolutions formats… fragmentation). They created a web view that would work on all tablet platforms.
What are our goals for a responsive design? Modules is the new way for developing sites. Little bundles of HTML and JS get pulled together to make a full website. This is done to isolate things in the design. SMACSS by Snook. We aren’t creating websites, we are creating systems.