on shared you would be best with hypercache and/or db-cache reloaded. Also there is a very important thing: drop all the image resize on the fly plugins/scripts. Make them run with a cron, or use wordpress-s implemented media/resize feature.
My site had a load of 5-13 on a vps (one core!). I dropped timthumb and with a script and cron i always upload the images from my index pages, and the few first blog pages to external imagehost (imageshack). Now my load is 0.5-1.3. The biggest problem was the image resize script.