Roger Hudson has written a detailed article called Accessible Forms using WCAG 2.0. The article provides practical advice about the preparation of accessible HTML forms.
More importantly, it compares the WCAG 1.0 accessibility requirements relating to forms with those contained in WCAG 2.0.
There are also a selection of movies where Andrew Downie demonstrate screen readers in action on specific aspects of forms. The videos are embedded in the article, as well as available here: