The following is an excerpt from The 7 Keys to Marketing Genius by Michael Daehn

People are willing to provide marketing information in exchange for certain benefits. My marketing professor was fond of creating events or concerts that were almost free. The only charge for admission was to fill out a response card. For example, he would stage a jazz music festival and get the names and addresses from the attendees. The response cards would ask if they were interested in receiving jazz music information and offers from vendors. After the event he had created a list of prequalified marketing prospects. Another way to trade for data is to have contests and giveaways that reward respondents with gifts or the chance to win a large prize.

Many early Internet sites gave away free products or information in exchange for registering with the site. Be careful not to give away the store or to create a climate where there is no possibility for paying for the expense of gathering the data. Many early Internet companies went bankrupt before they could take advantage of all the information they had gathered.