Forms are very important elements, especially to create accessible interaction. Yet, you should provide alternative mechanisms for forms. Although practically all browsers support forms, the support is often rather primitive. Despite all the measures we can and should take to make forms accessible, many people have problems with using forms.
In particular, if you have a form for sending feedback, requesting further information, joining an e-mail discussion list, or ordering something, consider specifying one or more of the following:
Make sure that the alternate contact methods really work and that the information on them is updated as needed.
Site search forms are different, since you don’t really expect to be able to have manpower for doing searches for users. In a sense, a good system of navigation is an alternative to using a search form. In addition, there should be a link to help with using the form, no matter how easy to use it might look. The help page or section can then contain contact information for problems with the form. The link could be, for example, visually an image consisting of “i” in a circle, with alt text like “info on using the search form.”