Frugal holiday shoppers will be happy to know that more and more retailers are looking into offering free shipping as an incentive to order from their online stores, but retailers need to carefully plan such promotions and be selective about when they offer deals and to whom the deals are offered, according to Free Shipping Report: Benchmark Data and Analysis for E-mail Marketers, a study from New York research company Experian CheetahMail.The study found 70 percent of respondents across all industries had higher conversion rates on e-mails offering free shipping than on other types of marketing e-mails. Of that 70 percent, 78 percent saw increased transaction-to-click-rates (defined as the total number of transactions divided by the number of unique visitors clicking on the e-mail), and 47 percent had higher average order values in free shipping e-mails compared to other marketing e-mails.To create the most profitable and successful free shipping e-mail campaign, Experian suggests that retailers:Feature the right products. Free shipping on overstocked items tends to perform poorly.Limit free shipping offers. Constantly running free shipping offers may dilute their effectiveness.Segment the e-mails. Divide the subscriber list into groups of customers based on their product interests, then offer those groups the products with free shipping.Retailers may also look to the second annual Holiday Free Shipping Day, slated for Thursday, December 17, 2009, to generate traffic. Free Shipping Day represents the last possible 24-hour period when online shoppers can place their orders with guaranteed delivery by Christmas Eve and aims to extend the online holiday shopping season, which typically peaks in early December because consumers are concerned about their gift orders arriving to their intended destination in time for Christmas.FreeShipping.org allows consumers to find online retailers that offer free shipping deals. For l...