First thing you should do to optimize your desktop site for mobile
Bruce Lawson has great post today called What Users Want from Mobile, and what we can re-learn from them. I highly recommend reading it.
Bruce quotes from a survey of mobile web users and pulls out a few highlights including a huge demand by users for performance. Bruce writes:
This tells us that speed is more important than aesthetics. So perhaps some of the time and effort put into media queries, viewports, avoiding scrolling, line length would actually be better employed reducing HTTP requests and optimising so that websites are perceived to render faster.
Exactly.
This echoes something Brad Frost and I were talking about the last time I was in New York.
If you could only do one thing to prepare your desktop site for mobile and had to choose between employing media queries to make it look good on a mobile device or optimizing the site for performance, you would be better served by making the desktop site blazingly fast.
Most mobile browsers are pretty good about providing tools to help someone utilize a design meant for desktop on a small screen. People can double-tap or pinch and zoom to see and read the content.
But if your site is a bloated mess, there is nothing people can do about it. There is no magical gesture that people can invoke to make something load faster if the developer hasn’t built the site for speed in the first place.
The only gesture they are likely to use involves a single, upright finger as they ditch your site for one that responds to their requests in a timely fashion.

Jason Grigsby is one of the co-founders of Cloud Four, Mobile Portland and Responsive Field Day. He is the author of Progressive Web Apps from A Book Apart. Follow him at @grigs.