Adding quicktags to wordpress
The long way is to edit the quicktags.js file. There’s an easier way: the WP-AddQuicktag plugin.
After activating this plugin, you get Options > Add Quicktags. That page gives you fields to directly add start and end tags that you use regularly. Then when you edit using the HTML instead of the wysiwyg editor, there’s a handy little button right along the others (like b, link, img, et cetera). Very handy indeed.