They leave work early. They never hobnob at the water cooler. They take long lunch breaks. In some ways, it's easy to spot the unhappiest employees at work. They tend to stand out in the crowd, especially if "the crowd" is joined at the hip during breaks, laughing it up after work, and even spending time together on weekends.

Yet there are a few more-subtle traits employees will exhibit when they are unhappy at work--and possibly about to leave their post. Here are the big ones.

1. They won't make eye contact

Not making eye contact with you is often a sign of someone who lacks confidence or is struggling with a personal issue. It doesn't always imply dissatisfaction with work. However, if the sales director in your company--the one who always seems jovial and confident--won't look you in the eye anymore and seems distracted, it could have something to do with him or her being unhappy and frustrated with work.

What to do about it
I used to have a boss who basically demanded eye contact during meetings. He'd even get up from the table, swivel his chair around, or crane his neck to make sure I was understanding him. To me, it was effective, because it showed he cared. It's not a bad approach with a disgruntled employee. It helps you get to the bottom of the problem.

2. They stop talking when you walk by

Huge red flag here. If you walk up to a group and one of the employees suddenly stops talking, it's a sign that person was complaining about something (and it was probably you). Not talking is a sign that the person is not quite ready to say what is wrong. Happy employees are almost always talkative--about the company direction, about their personal life, and about the joys of the job.

What to do about it
As a leader, you have to figure out how to get people talking again. Ask the right questions; force the issue. Schedule a meeting, or take a walk with the employee. The more you open up the communication lines, the more you will let information flow more freely--even the bad stuff. Then, you at least know how to take action and resolve the issue.

3. They ask endless questions

Having an employee who asks a ton of questions is not a bad sign--it sometimes just means you have someone who is inquisitive. However, asking a boatload of questions can also be a red flag when the employee is unhappy. They need more of your attention. They have a questioning attitude about employee benefits or company direction. Someone can ask questions for information (that's fine) or question your leadership (that's bad).

What to do about it
Of course, answering the questions is one obvious answer, but it won't help you get to source of the problem.  Having someone who questions everything is a sign of unhappiness. It's best to handle the issues directly and find out what is really bothering that employee. Resolve the issues, and you might save the employee relationship.