[CentOS] building CentOS rpms?

Hello,
	I'd like to get in to rpm building and am looking for a CentOS
specific document if any to get me going? I want to repackage an existing
rpm and give it different runtime options so it'll work on a server, and
make an rpm at least one probably more, and then submit them to the rpmforge
repo.
	Googling showed me some old Suse docs on this subject. Any help
appreciated.
	Thanks.
Dave.