"Great service" can mean different things to different people. As a good rule of thumb, think of a company that has provided poor service to you, and do the opposite of what they did, and beyond!
Small business owners, especially those without employees or administrative help, wear many different "hats" and are often rushed and overworked. Occasionally this can result in "mediocre" service for your customers. And even if you do have employees, they may be providing less than stellar service. Customers tend to not complain about "mediocre" service, since that is what we as a society have been conditioned to accept. So when a company provides a "great service", it will be remembered, and will help to solidify your company's reputation. A company with a proven reputation and excellent customer references can generally gain more business (and even higher prices) than a competing company that provides only mediocre service.
Great service includes, but is not limited to:
Although it may be tempting to "sway" a customer to purchase more services than he or she may need, resist that temptation. The customer will appreciate your honesty, will be more likely to refer you, may become a repeat customer, and may end up purchasing those extra services anyway.
You need to actually "care" about the quality of your work and your customers' satisfaction. If you're in business just for the money and you truly don't care about your work or your customers, it will show, and your company is more likely to fail.