Recently, a fast-food drive-through employee asked if I'd like dessert with my order. Since every combo-meal includes fries, it makes sense that these restaurants are cross-selling something else. Unfortunately, most cross-sell offers fall on unwelcoming ears. But, if a restaurant knows you're allergic to gluten or are on a low-carb diet, imagine how much more compelling and relevant their offer would be.

Sadly, bankers have comparable data and do nothing with it. When visiting my bank, I realized that I was preemptively declining a credit card offer before the teller had a chance to present it. Somehow, after ten or 20 offers, we both knew it was a perfunctory effort.

Cross-selling, as it once was, is mostly unsuccessful and can damage the customer experience. I've heard bankers bemoan the ineffectiveness of tellers at selling and I've heard tellers complain that they are required to make useless offers. The problem is that there are multiple obstacles to creating an effective cross-sell. The good news is that these obstacles can be overcome.

The problems boil down to a few constraints. Some customers are fundamentally unprofitable. Most of the time, we don't want to hear about an offer. Most offers are irrelevant to our life, and few customer service representatives are able to present offers in a compelling way.

The rule of thumb used by many bankers is that about a third of their customers are not profitable and that increasing wallet share for those consumers will just increase the loss. Even back in 2007, a Celent report noted that "customers' usage drives cost-to-serve and cost to-serve influences customer profitability." The first element of any cross-sell program is to segment consumers based on profitability and usage to avoid encouraging profit drain.

A more obscure, though intuitive, idea is that most of the time, consumers aren't receptive to an offer. Most marketers have heard about propensity models that purport to offer the right product to the right person. While these techniques are used by many digital marketers, they remain underutilized in the banking space. Think back to the fast-food example and the impact of relevance. Offering your clients the most appropriate product, based on lifestyle, current products with the bank (and other institutions), and family situations can yield a dramatic increase in acceptance. Much of this data is available within your banking systems without requiring a massive Big Data project.

Finally, the offers need to be well presented. There are a few factors that impact this, but the biggest is engagement. I'd bet that nearly every institution has at least one teller who starts the cross-sell pitch with "you don't want this product, do you?" They are convinced, based on experience, that the customer  will say no and are just trying to make it easier on the customer (and subconsciously easier on themselves). Providing a script that is tailored to each consumer's unique situation can dramatically improve the effectiveness of sales offers. Call centers have been doing this for decades, but live interactions are largely under-optimized.

Some will claim that many tellers still won't be up to the challenge. Will they present the offer with the consistency, enthusiasm and timeliness of digital channels? The amazing thing about humans is how well we respond to positive reinforcement. If a teller hears, "Yes, and thank you for offering that," they will be much more enthusiastic during the next offer. If they hear "yes" 1-out-of-3 times, instead of 1-out-of-20 times, they will be much more effective. The problem isn't that the tellers can't cross-sell. It is that they aren't given a quality offer to make.

The key factor in cross-sell success is utilizing all of your resources to make the right offer, to the right customer, at the right time, in the right way. Done well, cross-sell really does matter. Larger institutions are making great strides and digital channels are starting to become profit centers using these techniques. In the coming years, successful banks will need to change their thinking on cross-sell to maintain their edge. Using the right best practices, cross-sell can still deliver profitable wallet share and allow your weakest teller to rival your most skilled seller.

Eric Lindeen is marketing director for Zoot Enterprises Inc., a provider of loan origination, account acquisition and credit risk management solutions for large financial institutions. You can follow him on Twitter @EricLindeen.