We can’t fault you for focusing on adding customers to grow your business. In fact, it speaks to the ambition that drove your business to the success you currently enjoy. But as the year wraps up and you’re running out of time to sign new customers, we’d like to redirect your focus to the people writing your paycheck each month—your current customers.

We’ve all heard over and over again that it costs more to add new customers than to keep existing ones. That makes upselling to your current customers critical to keeping your business in the black. Upselling keeps you relevant to customers even after you solve the problems they initially came to you with, and it makes your business relationship more profitable.

So rein in your marketing efforts toward the client you already have. Keep reading for four tips on increasing sales with upselling.

Be Inclusive
If you assume that your customers are aware of all of your products and services, you’re only hurting yourself. It’s not their job to assess what they need from your business’s suite of services. It’s yours. So don’t just market new services to leads. Include current customers in your mailing list when promoting a special. Alert clients to the new product you just rolled out. Never underestimate the potential for new business in an old client.

Happy and In It for the Long-Haul
Not losing current clients is too humble a goal. Not only do you need to keep them, you need to keep them happy. Offer customers training and support to help them get the most out of the products and services you sold them. The trust you’ll build by taking the time to educate them will prove invaluable when their looking for upgrades down the road.

Just Checking In
Make it a priority to stay on current customers’ radar, because so much of the upsell depends on your being attuned clients’ every wish or need. Keep in touch to stay in the know about the challenges they face, their changing target audience and their biggest worries as a business. Talk to customers regularly. The conversation should be a low-pressure, sales pitch-free discussion about their problems. Listen to them carefully then identify upselling opportunities consistent with their needs.

An Elephant Never Forgets (But Clients Do)
Remind customers of all your company offers to help their business grow. Write a personal letter to clients in whom you see potential for spending more on your services. Include a list of everything your business offers, with the products they’ve already purchased checked off. It’s a subtle way to show clients that you can fulfill more of their business needs, even ones they might have missed.

Share these ideas for increasing revenue through current clients with your sales and marketing team. Focus on the art of the upsell for a last-minute boost for your 2011 income.