Ok....you can do this using any of the following ways:
1. You can place your executable shell scripts under /etc/rc.d/init.d. All the scripts in this directory are run when the system starts up.
2. ( The Better option)
Make your scripts executable and put them under the directory /usr/local/bin
Now in the /etc/rc.local script, call your scripts one by one. For your reference, I am posting my own rc.local script which calls another script (load_sound_tv_radio.sh) that loads the modules for sound and tv.
# This script will be executed *after* all the other init scripts.
# You can put your own initialization stuff in here if you don't
# want to do the full Sys V style init stuff.
[You can call your custom made scripts here]
Hope that helps