The first thing to show to a client when starting a co-opearation regarding a Joomla! 1.5 project is how he adds his content.This is fairly easy once you do it a couple of times and it is also the backbone
of the project's success.
Joomla! ever since its birth has a special philosophy behind it that either you get used to it or you dont use Joomla! This is: Everything is based on ids and content is separated from Menu Items. Also, unlike other CMS's you cannot create the menu item and the content item from the same place.
You first create your item and then you create your menu to it.
In the video below you can see how to create a content item in Joomla! 1.5 and link it from the menu. Enjoy!