Lets hope you're running Apache and not IIS...
Here's some mod_deflate to get ya started. It can go in your httpd.conf or apache2.conf files (depending on apache version). It also assumes you enabled mod_deflate. At the very least, google these directives and it'll lead you to some good examples.
Code:
AddOutputFilterByType DEFLATE text/plain
AddOutputFilterByType DEFLATE text/xml
AddOutputFilterByType DEFLATE application/xhtml+xml
AddOutputFilterByType DEFLATE text/css
AddOutputFilterByType DEFLATE application/xml
AddOutputFilterByType DEFLATE image/svg+xml
AddOutputFilterByType DEFLATE application/rss+xml
AddOutputFilterByType DEFLATE application/atom_xml
AddOutputFilterByType DEFLATE application/x-javascript
AddOutputFilterByType DEFLATE application/x-httpd-php
AddOutputFilterByType DEFLATE application/x-httpd-fastphp
AddOutputFilterByType DEFLATE application/x-httpd-eruby
AddOutputFilterByType DEFLATE text/html
#Highest 9 - Lowest 1
DeflateCompressionLevel 9
#Optional
#Skip browsers with known problems
BrowserMatch ^Mozilla/4 gzip-only-text/html
BrowserMatch ^Mozilla/4\.0[678] no-gzip
Your sites will AUTO compress/decompress on the fly. You can check with firebug if the data was gzipped when it arrived to the browser.