Online retailers used new tactics to boost sales during the end of year holiday shopping season, according to the results of a mystery shopping study conducted by the e-tailing group.

The e-commerce consulting firm said retailers using the same old practices from year to year have reason to fear, as more and more shoppers will turn to vendors with more innovative sales charms.

To provide guidelines to help conservative retailers snap put of their doldrums, the e-tailing group provided a list of metrics culled from 100 retailers showing what perks may have led to improved sales from 2003 to 2004.

"To achieve best-of-breed status, merchandising tactics need to be customer-centric and multi-channel," said Lauren Freedman, President, the e-tailing group, inc.

For example, advertising Internet-only sales was a key way to garner new customers and sales for 14 percent of all retailers surveyed. Incentives such as buy one/get one free, or a savings on the next purchase were also used by 23 percent of the merchants in 2004 versus 12 percent in 2003.

Though an age-old standby, suggestive selling also proved popular among vendors to boosting purchase orders. Forty-nine percent of sellers upsold last year versus 22 percent in 2003. The number of retailers who issued recommendations in the shopping cart stage also grew from 50 percent in 2003 to 56 percent in 2004.

Outfits used viral marketing to spread word of the goods they sold, with a quarter of retailers asked saying they provided a forum for customer feedback to sell products.

Sixty-one percent of retailers surveyed offered a holiday shipping deadline in 2004 as opposed to 56 percent in 2003, while more companies offered conditional free shipping as the Christmas deadline grew closer.

Also, 86 percent of the sites in 2004 offered gift certificates or gift cards compared to 77 percent in 2003. This highlights a convenience factor for time-constrained consumers who may not have time to shop traditional brick-and-mortar stores. More sites also offered gift wrapping in 2004 than in 2003, 55 percent to 50 percent.

In other valuations, the study determined that it is crucial for retailers to use a manufacturer's "brand" as a selling point and that aggregating products by vendor is becoming more important: this was done by 83 percent of retailers surveyed in 2004, versus 75 percent in 2003.

Offering exclusive products is another way sellers can differentiate themselves, with 26 percent hawking goods unavailable elsewhere in 2004, as opposed to just 13 percent in 2003.

This article originally appeared on InternetNews.com.