1 - Run a speed test on your page.
2 - Choosing Best Web Hosts for your Wordpress Blog
3 - Configuring Apache for Maximum Performance
4 - Upgrade to latest WordPress Version
5 - Delete unwanted plugins & upgrade to latest plugins versions
6 - Install WP Super Cache Plugin
7 - Install PHP Speedy
8 - Install WP CSS
9 - Install DB Cache
10 - Install Optimize DB
11 - Using Google AJAX Libraries API
12 - Optimizing your Mysql Database
13 - Using Amazon S3 Storage service
14 - Optimize your images
15 - Minimize PHP and database queries
16 - Optimize CSS & HTML & Javascript size
17 - Cache Gravatars
And read full the article:
http://www.chotoan.com/wordpress-speed-up/