Which log file lists the activity of startup scripts, particularly loginhooks? I am trying hard to find it and I cannot. How can I even tell if my script is running without errors if there isnt a log? Very frusturating!

It is up to you to use whatever log file you want to return success and/or failure information.

In your LoginHook, use the "logger" command to send the status to /var/log/system.log

You could start your script with a simple "running LoginHook" to determine if the hook is actually getting called successfully. Then you can test for success or failure of the various operations in the LoginHook script by testing $? after each, and report based on that.

So:
logger -p local0.notice "LoginHook: LoginHook started at "`date`

at the beginning of your LoginHook would indicate it started nicely.

Entering additional LoginHook task success or failure really helps troubleshooting, so
logger -p local0.notice "LoginHook: yourcommandhere OK/failed "`date`

man logger