DOCBOOK-APPS: simle examples

Hi,

Where can I get some simple, but complete, examples about how to 
customize the StyleSheets from DocBook ?

I've try to read the "DocBook: The Definitive Guide", but it's examples 
are useless: they don't have the complete commands or where should I 
save the code and how should I name the dsl file and then how to invoke it.

What I really want is:

- where can I define my new tags (like <my_book>, <my_bold>, <my_title>, 
<my_list>, <my_list_item> elements) for HTML, PDF, and TEXT;
- where can I undefine tags I don't use;
- how can I reference the above stuff from my SGML file;
- how do I generate the final HTML/PDF/TEXT outputs using my own styles 
(what's the command line to process my sgml file ?)

For example, I'd like to be able to process in the end this simple file:

<my_book>
<my_title>xxx</my_title>
<para>xxx <my_bold/yyy/
<my_list>list
	<my_list_item/item1/
	<my_list_item/item2/
</my_list>
</my_book>

What should I add before the <my_book> tag ?

TIA,

Ionutz