Have you ever been blindsided by the sudden departure of a key employee?

It can exact a heavy toll on your business--especially if yours is a startup or smaller company operating with few employees.

The employee who hands in a resignation notice might be crucial to keeping a key department or operation running smoothly. The departure could strain other workers who were dependent on the leaver in order to perform their own jobs effectively. The void could be felt for months--even affecting the company's profits.

And you know how much time, expense and effort it takes to recruit, hire and train replacements.

Retaining your most important staff members starts, as with all new hires, by offering competitive pay and benefits. That should include a 401(k) plan with some amount of employer matching contributions. In today's competitive industries, any company that doesn't provide a 401(k) or other tax-deferred retirement plan is at a recruiting disadvantage. My company has been ranked multiple times over the years by several publications as one the best places to work partly because of the compensation packages we offer.

Compare your package to companies you compete with (for both talent and customers). If you're not offering similarly generous packages, you can expect higher than average--and perhaps higher than acceptable--levels of turnover.

And turnover is a key metric. Recruiting, hiring and training is not only costly in terms of time and money, but it also can hurt you through missed opportunities. See if your employee turnover rate is higher than it is for competitors.

When employees do leave, interview them. Find out why they left. You'll discover it's not always--not even usually--about the money. Employees often quit out of frustration--with the job, co-workers, or even their boss. Many of them are reluctant to speak up, so it's important to get them to talk openly and honestly when they depart.

And try to get people to tell you how they feel long before they decide to quit. In addition to an annual performance review, try talking with employees informally during the year.

Find out what they like most about their jobs and what they like least. To phrase it more subtly, you might ask which operations or tasks they'd prefer to handle more and which ones they'd rather encounter less often if that were possible.

That information can help you adjust job descriptions and assignments that enhance the positives while reducing the negatives that create frustration for those you value most.

And remember to praise people. "Thank you" and "good job" are often more highly valued than a 3% raise, so be sure to praise people for their performance and contributions.

You can't create the perfect work environment for everyone, but engaging with your employees more often in a relaxed, informal way can help you keep more of them for a longer period.

At least it should keep you from getting blindsided with a resignation notice.