I bet you did not know there was a "Get to know your Customer Day". Well neither did I. It is actually observed annually on the third Thursday of each quarter (January, April, July, October) not just once a year. But this is a good time to mention something you should be trying to do all the time. Because the more we know our customer the better we can sell to them and service their needs. Plus touching base with your customers every quarter is a great way to keep on their mind and get referrals even if they do not buy services again from you at the time.
There are some things you can do to make your customer feel appreciated and wanting to spend more with you. Write a personal note of thanks: everyone likes to know you like them as a customer and if has been proven that a simple handwritten note or post card can do a lot. Be sure that you are just saying thanks, not trying to sell them, use pretty stationary not strictly business printing.
Send those customers that spend above a certain amount a small swag gift or a gift card. It can be something as inexpensive as a $1.00 koozie or a $5 card to Starbucks (if you know they drink coffee, which I do not).
You can discount a customers sale for long term loyalty, for instance 10% off at their customer anniversary. Or give them a percentage back for each year they have been a customer on their anniversary.
Choose one customer a quarter to highlight as a case study on your website, Facebook page, in a news letter or other way. Focus on the job you did for them; how you turned a negative into a positive, how a problem was fixed, how you came to the rescue for a customer, did a job free for a non profit, worked with an organization on a cleaning project. These personalized write ups can bring attention to certain aspects of your business not everyone may know. Can bring great SEO to your business and gain you new customers.
Make sure you have an use a customer referral program. Satisfied customers are your best selling asset and Never forget, you do not have a business without your customers.