We all know that customer service is important. Serve customers well, and they're likely to keep coming back or even tell their friends. Treat them poorly, and plenty of people will hear about it.

As investors, we can find that it's profitable to follow which companies are known for great service, which are improving their service, and which are not doing so well. To that end, here are a few companies recently singled out as among the best and worst in customer service by the folks at crmlowdown.com:

The Best
No. 1: 1-800-Flowers (NASDAQ:FLWS). The company works to stay sufficiently staffed even during peak times by hiring teachers and retirees seasonally. Pay is reportedly performance-based, a motivation for representatives to please customers.

No. 5: Southwest Airlines (NYSE:LUV). The company is praised for offering high-level service, even though it's known for minimizing costs. Part of its success might be due to its flat organizational structure, with few layers of management. This can help employees feel less like minor players. Southwest also has a high level of employee ownership, and owners are clearly more motivated to help the company succeed.

No. 9: American Express (NYSE:AXP). Here's an eye-opening tidbit, in our day and age: according to a reader, "No matter what hour of the day, you always get a live customer-service rep.!"

The Worst
So which companies were awarded the lumps of coal? Here are just a few:

No. 1: Dell (NASDAQ:DELL). Poor Dell has quite a bad reputation in this department, though I often run across anecdotal evidence to the contrary, such as my own experience with the company when my hard drive died. Warranted or not, the reputation is there, and it isn't an asset. The company has acknowledged that it's working on the problems. If it pulls off a turnaround, market share might benefit.

No. 3: Time Warner's (NYSE:TWX) AOL. What makes it bad? Well, it's reportedly very difficult to cancel your service. It's hard to find phone numbers to call, and even if you do, it can still be hard to get through to the person who can help you.

No. 9: Home Depot (NYSE:HD). The retailer placed last among major U.S. retailers in the University of Michigan's annual American Customer Satisfaction index. Investors can wax hopeful, though, as the company is taking steps to improve its service, such as trimming its HQ staff and beefing up its customer-service staff.

Your thoughts
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Longtime Fool contributor Selena Maranjian owns shares of Time Warner and Home Depot. The Motley Fool has a full disclosure policy.