Drip marketing (aka. drip emails, or lead nurturing) is often used by modern marketers to nurture their leads through the sales funnel. As others have mentioned the idea is to gain brand awareness and influence buyers through a regular series of targeted and relevant content or offers. Typically for top of the funnel activities you might offer something like a general whitepaper or something which describes the overall business problems that your prospects might be feeling. From there you can use a marketing automation tool to send through additional material or reminders periodically depending on how your prospects engage with you. The idea at the end of the day is to reduce that amount of direct time that a sales rep spends closing any deal by ensuring that leads have shown sufficient buying signals and are ready to purchase.

I think the answer to this is very much about customer engagement. It's all about speaking directly with your customers and really listening to them. If you are prepared to listen and react to them, they are often more interested in reciprocating. You've also not got to be afraid to guide them if you want them to talk about your product. Suggest to them that if they like something that you've done that they share it on Facebook, LinkedIn or other social site. One of the best forms of engagement is a great customer support department, they are on the front line talking with customers daily and can really be your best brand advocates.

Give the user a reason to want to complete the form in the first place. Like others have said don't be afraid to give your visitors a taster of what's to come in the form of a partial book or a screenshot of your Whitepaper. You might also want to think about other techniques that are commonly deployed in online stores to get people to purchase. So think about things such as allowing users to rate or comment on your content so that other visitors can get unbiased opinions before they download. You should also use things like progressive profiling so that you are only ever asking for minimal information at any one time, this reducing some uncertainty people have about giving away their personal details.