The most important is this rule of thumb: the more fields you require prospects to fill in to get your content, the fewer of them that will ask for it.
Therefore, make mandatory only those fields that give you the information you absolutely need at this juncture in the sales cycle. Other fields should be optional.
Q: What free content format is best?
While there is no "best" free content offer, today free e-books are popular and working well. These e-books are downloadable PDFs.
Bob Bly is a freelance copywriter who has written copy for more than 100 clients including IBM, AT&T, Praxair, Intuit, Forbes, and Ingersoll-Rand. McGraw-Hill calls Bob “America’s top copywriter” and he is the author of 90 books, including “The Copywriter's Handbook.” Find him online at www.bly.com or call (973) 263-0562.