Testing and correcting accessibility problems throughout the development process is all about tools. Here are tips I've collected:
- Support the fewest back versions of JAWS you can: just as with browsers, supporting earlier versions makes development infinitely harder. Current version is 11.
- Fangs is a free screen-reader emulator, a Firefox plugin: http://www.standards-schmandards.com/projects/fangs/
- Use Juicy Studio accessibility plugins and toolbar: https://addons.mozilla.org/en-US/firefox/user/320.
- WebAIM now has an accessibility toolbar: https://addons.mozilla.org/en-US/firefox/addon/6720.
- There's also a free Web Accessibility Toolbar for IE: http://www.paciellogroup.com/resources/wat-ie-about.html
Finding more tools: