I've grown my companies by focusing on great customer service. We didn't always have the biggest names in business working at the firm, and we sure couldn't always afford the flashiest equipment. What we did better than all our competitors was ensure that our customers were thrilled.

In fact, superlative customer service can be your very best (and cheapest!) form of marketing. Customers talk about their experiences, especially if those experiences are unexpectedly good. Sometimes even the most difficult situations can yield satisfied customers, depending on how you and your team handle the problems that arise. Even a failure to meet expectations can offer an opportunity for a great recovery and a happy customer.

Here are four phrases that will help you bring up the level of service your customers receive:

1. "I don't know, but this is what I'm going to do."
You're not always going to have the answer to every question at your fingertips, and your customers will understand that. What they expect in exchange, though, is honesty and follow-up. The key here is to make a clear commitment like "I'll call you by 5 p.m. with the answer," and then keep that commitment!

2. "I am very sorry."
When you or your company has made a mistake, the customer wants to hear you accept responsibility and apologize. Too many customer service reps have been trained not to accept responsibility, in some cases because they fear the legal record of having admitted failure. Realistically, though, the probability of a lawsuit is minimal, while the chance of losing a customer is virtually guaranteed. The apology is only a step, albeit an important one, and the goal is to turn the failure into a success by determining what your company can do to make it right.

3. "Yes."
"Yes" is what your customer wants to hear, and your goal should be to say that word whenever possible, even if – especially if – you're working through a problem. Customers want progress. Say yes to reasonable requests as soon and as often as possible, and leave your customers pleasantly surprised at how easily the problem was resolved.

4. "Is there anything else I can do for you?"
Here's your perfect wrap-up. Not only does this question give your customer the opportunity to bring up additional concerns, but it also lets the customer feel like they're in control. They can ask for additional information or they can thank you for your spectacular service.

Great customer service relies first and foremost on authenticity, and being trustworthy is the foundation. If your customers trust you to keep your word, then you're more than halfway there. If your customers know they can rely on you, even if there's a problem, that's the rest of the journey.

Work on training your customer service reps to listen, determine what the customer expects and do what they can to make sure that customer is satisfied.