Every cpanel server should be need to optimize according to your server usages, I hope the following articles will help to improve your cpanel server performance.

Run your cron jobs at off peak hours.

Stopping SpamAssassin

Go to WHM > Server Configuration > Tweak Settings > Disable Spamd

And:

Go to WHM > Service Manager > Disable Spamd

Disable Anonymous FTP

Go to Service Configuration =>> FTP Configuration

Stopping Mailman

If you or none of your customers aren’t running any mail listings through cPanel, it would be a good idea to disable Mailman.

Go to WHM > Server Configuration > Tweak Settings > Disable Mailman

Catch all can use up many resources and storage space, To disable CatchAll

Go to WHM > Server Configuration > Tweak Settings > Change to :fail:

Tweak Apache to reduce lot of memory.

vi /etc/httpd/conf/httpd.conf

Change the following settings depending on your server usages.

MinSpareServers 5
MaxSpareServers 10
StartServers 5

Save and restart apache now.

/etc/init.d/httpd restart

Install PHP accelerator (Recompile Apache with eAccelerator)

Compiling Apache with mod_deflate Gzip Module

Turn Off unwanted statistis

Analog Stats, etc.,