Need help customizing sudo

I've been trying to customize my sudo command so that I can gives guests and friends admin accounts but restrict their root access privileges. The man page "man sudoers" is a little too dense and is somewhat lacking in examples. Can anyone give me a good online referrence (sudo.sw is identical to the man page) or an example or two applying some of the syntax? Thanks.

If you don't activate the root account and hence don't set a root password, can't anyone with administrative priveleges access a file with root ownership using the sudo command paired with their password? This leaves me wide open to pranks.

Normally the first account that is created, has administrative privileges. Another other accounts that are created would have to have the admin flag enabled, then there pass word would work.