Few more things to add from my experience. Most of the time when the application is developed we do not consider the advanced techniques like domain sharding , lazy load, DNS prefecth, minification and compression.

1. Domain Sharding:
All the browsers has a limitation on the number of connection to one domain , so it means if we push all the objects from the same domain the site will be slower. to make the site faster with you can use multiple domains to serve the contents. for example , for the images you can create a subdomain with images.yoursite.com , for js you can use js.yourdomain.com this will help to serve the contents faster with parallel loading.

Apart from that where ever it is possible to load the static objects from the cdn use it. for jquery you can use any of the CDN with the better performance (maxcdn, google code or jsdelivr).

2. Lazy Load:
Applying the lazyload mechanism will put some delay on the images loading and your site will have the visibility little quick. In other terms all the objects should not be loaded at the same time. Load only the objects that are required.

3. DNS Prefetch:
DNS prefect will help the site to reduce the DNS lookup time. Make sure to add all the domains / sub domains used in domain sharding are in the prefetch.

4. Minification:
Always use the minified version of the CSS and JS files for the site. Unminified files always creates a big impact on the site performance

5. Compression:
Do not limit the compression for the CSS, JS and HTML only. Use the compression for the images as well. Using the progressive image compression will help the site to be loaded faster.