another (potentially) essential config tweak:
if you are running high-traffic sites, and especially if they sit on a cloud Vserver that usually have limited storage and limited I/O bandwidth, you want to disable the Apache Access log:
http://www.howtoforge.com/forums/showthread.php?t=52180
just use google analytics or another stats provider for stats. they are better anyway - and won't clog your server with 30+ Gigs of logs, hello backup storage!