Perform split A/B testing of your lead generation form, the same way you would with a landing page or ad copy, and try to eliminate as much clutter (fewer mandatory fields and personal questions) as possible with each test. Foster also says that testing the layout of the form (such as whether you use drop-down menus or "choose one" radio buttons) should also be part of the optimization process.
Lastly, make sure to tie the user's submission of this info to an immediate and obvious benefit--either access to a member's only section of the site, entry into a contest, or whatever is relevant to your target market. And try different iterations of the "submit" button, both with characteristics like size, shape and color, as well as the actual copy on it. Foster says that using phrases like "Tell me more" and "Send me my [incentive]" can go a long way toward getting your clicks to turn into actual conversions.