Most of the scripting websites have their own web boards of some description:

http://www.mircscripts.org/forumlist.php
http://www.mirc.net/forums.php
http://www.mircscripts.com/phpBB/index.php
http://www.hawkee.com/phpBB2/index.php

There are also a number of Tutorials sections on those websites which contain many documents on many areas of mIRC scripting:

http://www.mircscripts.org/archive/tutorials
http://www.mirc.net/projects.php?go=tut
http://www.google.com

You could also look for code snippets, which are a practical way to learn how to script. General experience is the only true teacher though...

Regards,