This is a short article mostly optimized for use with WordPress.

First, very simply insert this into your virtual host config file (probably in /etc/httpd/conf.d or in /etc/httpd/conf/httpd.conf if you’re using the basic Apache setup config file for the host):

#Let's set to gzip all apache's output
SetOutputFilter DEFLATE

#let's exclude the following file types
SetEnvIfNoCase Request_URI \.(?:exe|t?gz|zip|iso|tar|bz2|sit|rar|png|jpg|gif|jpeg|flv|swf|mp3)$ no-gzip dont-vary

#set compression level
DeflateCompressionLevel 9

#Setup browser specific compression requirements
BrowserMatch ^Mozilla/4 gzip-only-text/html
BrowserMatch ^Mozilla/4.0[678] no-gzip
BrowserMatch bMSIE !no-gzip !gzip-only-text/html
SetEnvIf User-Agent ".*MSIE.*" nokeepalive ssl-unclean-shutdown downgrade-1.0 force-response-1.0

Other than this, it’s pretty clear.

Make sure you have the LoadModule deflate_module modules/mod_deflate.so uncommented in the /etc/httpd/conf/httpd.conf file!

service httpd restart

and good luck!