i asked the same question in another post, upgrade to dedicated server or vps ^_^ also dont use large images and do not use chat plugins also there are some plugins available like garbage collector i would like more ways too i can not remember were i posted the posted.

also use cron jobs if you can

http://community.elgg.org/discussion/view/1129767/how-to-speed-up-my-site

Thanks UK.

youe most welcome : )