As you gather this information and provide them with valuable content that helps solve their needs (or even open their eyes to a need they didn't know they had), you can start asking for more information from them. Consider making some fields required; usually these fields are identifying information and information you need to categorize your leads. Other fields make optional; these fields are the nice-to-haves but aren't required to help you segment. In conjunction with smart fields and progressive profiling, your ability to remove fields of known data and replace it with new data makes form submissions easier for your existing contacts.
Like all documents though, electronic forms are not automatically accessible. Key considerations when creating an electronic interactive form are: Labels and prompts must be explicitly associated with the fields they represent. Otherwise, users who can't see the form may be unable to tell which labels and prompts accompany which fields.