General :: Runlevel Scripts And Creating Links?

I have learned without a doubt what runlevels are...the questions I have are related to the init scripts and how to create a link to an init script. I see that there was a post where someone was trying to get people to do homework for them...I assure you I want to understand what I am trying to learn. That said, here are my hang ups:

1. The script that contains the default runlevel to my understanding is /etc/rc.d/init.d, though I've also found /etc/inittab on the web as the default. My book isn't too clear on this as it doesn't state it exactly, so which is it for sure?

2. My assignment asks what I'd name a link to an init script that would start a fictitious BIGD daemon early on in the boot process. My answer: /etc/rc.5.bigd.d --I don't think that this is the right answer though because in the book, it states that the /etc/rc.d/rcN.d contains names of scripts whose names begin with K and S. My understading in that this starts and kills each script depending on how it's entered.