If you've got the prize right, the rules right, the type of competition right and the promotion sorted - then you're well on your way to a successful prize draw.
But what else can you do to make it better?
1. Make sure your 'Thank You For Entering' page isn't blank. Use it to promote your products, offers, discount codes or some other promotion. If there's nothing of interest on the thanks page the liklihood is that the visitor may leave your site.
2. Send users a thank you email when they enter (include an offer to further remind them of your brand).
3. Don't give all users a "discount" as a prize. If you want to offer a discount to competition entrants offer it as a "thank you". Discounts are not prizes.
4. Don't let people cheat or take advantage of your competition.
5. Announce the winners, publish a winner's list and send out the prizes!