Steve Souders has jolted down fourteen simple tips and tricks to improve website performance.
- Make fewer HTTP requests
- Use a CDN
- Add an Expires header
- Gzip components
- Put CSS at the top
- Move JS to the bottom
- Avoid CSS expressions
- Make JS and CSS external
- Reduce DNS lookups
- Minify JS
- Avoid redirects
- Remove duplicate scripts
- Turn off ETags
- Make AJAX cacheable and small
You can download his complete presentation on the said topic at Web 2.0 Expo conference from here
For a detailed description of each of the above 14 tips refer to Exceptional Performance section at Yahoo Developer Network.