Modifying system startup

I feel pretty much like an idiot, but here goes:

I've read in multiple places about how Tru64 Unix performs system
startup. I understand pretty will the relationships between inittab,
/sbin/init.d, and the various rc.0/2/3 directories.

What I can't seem to find is good documentation on the exact steps one
takes to add your own startup script. In this particular case, I have a
very simple shell script I want to execute at startup that just
reallocates which systems in a cluster are managing the various mount
points, using the cfsmgr command. 

I've already written the script and it works fine standalone, and I'm
sure I can play around with this until I figure it out, but I was
thinking there'd be some clear documentation out there that tells
someone step-by-step what needs to be done.

If someone could "connect the dots" between the academics of how the
startup process works and how the heck I get my script to execute at
system startup I'd be most appreciative!

Much thanks!!

Chris