There are many good resources on the Web that can help walk you through this process. Planning a good entry form for your sweepstakes will yield you better results for your goals. The information you request should be formulated from your goals. It's perfectly acceptable to ask questions about consumer preferences on your entry form, such as brand name awareness or shopping habits. Be aware, though, that if you ask for information that is too personal, such as income level, you may not get a large response.
People are still very wary about giving out that sort of information-with good reason.
Even if you represent a very well-known company, people aren't going to divulge a lot of personal information. Also, don't arbitrarily assume that because people enter your sweepstakes that it's acceptable to contact them with other product information. Provide a check box on your entry form so people can choose whether they want you to contact them with offers, notices, or special discounts in the future. Sending them unsolicited e-mail just because they entered your sweepstakes is akin to sending spam. Your second promotion will most likely be a lot less successful, because people will know that you are just collecting names to send them unwanted mail at a later date.