Targeting isn't solely reserved for display advertising. Here's how to use consumer behaviors to deliver relevant content to your email subscribers.

The majority of online retailers still send the same single email offer to every subscriber on their contact list. This all too common practice may generate what the company considers an acceptable level of return, but it also has a number of lasting negative side effects. Revenue is being left on the table, and disinterested recipients tune out and unsubscribe -- and these consumers are quite costly to recoup.

Savvy marketers know that not all customers are motivated by the same product and price point, so sending more individualized offers generates better results. It is not a matter of marketers not knowing what to do to make their email campaigns more effective -- it is more a question of how.

Here are a few quick and easy ways that online retailers can spruce up their email campaigns to make them more targeted and more relevant. These tactics do not require a large investment in time or resources and can mean the difference between an average and an outstanding email marketing campaign.

Notice nuances
Knowing what people ultimately purchase is valuable, but knowing everything that caught their attention along the way is priceless. If you examine "micro-behaviors" such as search, zoom, clicks and page views, you have a more accurate picture of what your customers really want. When consumers shop online, they leave a trail of data that indicates every action they took on your website in relation to every product.

For example, by analyzing this data, you can learn which segment of your customer base is interested in a cashmere sweater in gray. Whenever you send those customers an ad for the sweater, you will picture it in gray.

Also, if you studied your customer's micro-behaviors and learned that 30 percent of those who bought a pair of dark-wash skinny jeans also purchased a black leather tote bag, then you should not send an ad for one without featuring the other. Use this knowledge to make your email campaigns, as well as all of your marketing programs, more effective.

Use "null" to your advantage
More and more marketers are including search boxes in their email campaign creative. Unfortunately, customers sometimes search for items that are not available. By anticipating this event and offering suggestions on null search results pages, you create another chance to cross-sell comparable items to interested customers.

Do not ignore the auto-email
When order confirmation emails go out to customers, use the opportunity to cross-sell merchandise. Basing the cross-sell products on behavioral data will give you the best return.

Say thanks with an offer
Does your website have a “share with a friend” functionality? If so, you have the opportunity to thank the sender for spreading the word. Use this behavior to introduce a new product or offer in an email as a way of thanking the customer.

Opt down instead of out
Do not present customers with do-or-die subscription options. Instead of forcing them to sign up for one -- or none -- of your email lists, give them choices. Although they may not be interested in receiving an ad in their inbox once a week, they may appreciate knowing what is new via a monthly email ad.

Not only will you will find that customers appreciate the ability to opt down instead of out, you will save yourself the expense of finding new subscribers to replace those who felt overwhelmed.

Online shoppers are offering up terabytes of data that outline their behaviors and interests. By following through with the previously mentioned practices, you'll have a keener understanding of these behaviors and the insight to send your customers offers and promote products they really want. In turn, your customers will become more receptive to your emails, knowing they contain items that they actually want and need to purchase. After undertaking this new approach to consumer emails, clickthrough and conversion rates can increase multifold while unsubscribe rates substantially decline.

Sheldon Gilbert is the founder and CEO, Proclivity Systems.