Here are some tips that are useful in Wordpress optimization and better performance. It will reduce the CPU burden by Wordpress on the server.
1)Upgrade your WordPress to the latest version if you havenít.
You are probably reluctant to upgrade if itís already working but note that every WordPress update always contains bug fixes and improvements so there is no reason not to upgrade.
2) Remove all the plugins.
I know the plug-ins are nice. Are you sure you really need those plug-ins?. If you don't need them, just delete it only use the inevitable one.
3)Only activate plug-ins when you need them.
For example, you donít need to activate a Theme previewing plug-in if you are not planning to change a theme. You donít need to activate a WordPress database backup plug-in if you are not auto scheduling a backup, and so on.
4)Install WP-SuperCache if you havenít. [Most Important One]
It is clear that the wp supercache has great performance while having the lowest overall resource hit on the server. It should always be using the leastamount of memory and CPU time that it possibly can.
5)Reduce PHP/Database calls as much as you can.
Most CPU usage is caused by the number PHP and database calls. Using WP-SuperCache helps this tremendously but sometimes it canít be helped that your blog still has to do some PHP/Database calls. If you can reduce it though, do it. For example if a plug-in allows you to set an option whether to write a logor not (like number of spam comments caught, etc), then disable it. This will reduce the number of database insertion/update calls.
6) Reduce the number of Widgets and other components as much as possible.
Although putting a weather widget or other widgets are cool, do you really need them? Besides cluttering your blog and turning visitors off it can also put a strain on the server. Turn them off!
Your database has been updated a lot of times in the last day, whether youíve posted or not. Thereís a lot of chance for errors there.
The process can be completed through the cPanel.
a) Under the Databases section, click on PHPMyAdmin -->> Select your wordpress database.
b) Notice the table that appears. This contains all your posts, categories, comments, blogroll links, users, etc.
c) Scroll to the bottom. Click on Check All.
d) To the right of Check All youíll find a drop down. Choose Repair
e) Repeat the process and choose Optimize from the menu.
(Note that you really only need to do this if you have a lot of overhead in your tables. Check it often.)
Close any Post Writing Pages when youíre not using them.
WordPress will Auto-Save and it uses server resources and builds up CPU usage.
9) Turn off the Formatting Options in Settings
In WordPress, under Settings->Writing uncheck both Formatting options. Especially turn off ďWordPress should correct invalidly nested XHTML
10) Donít post via e-mail/word.
Write your posts in the Write interface and copy/paste it into Word when youíre done or when you take a break.
Donít make WP spend time parsing your Word file.
11) Use Summaries in Feeds. Under Settings->Reading, select use Summaries in Feeds.
12) Under Settings-Discussion, turn off any e-mail notifications you donít need;
especially redundant ones.
If you go to your blog often, donít worry about having it e-mail you for comments. Just turn that off.
13) Reduce image/video/flash/etc sizes. Use Photoshop, Gimp etc to reduce the image size.
14) Rename the file wp-cron.php to wp-cron.php.bak
15)If all else fail, switch to a simpler theme and definitely it will reduce the CPU usage.