Many people become managers because they're good at the position they will be managing. In some cases, bosses might get hired because they succeed in sales -- an area that's vitally important to most companies but not always a way to foretell good managers.
What's often missing from how many companies pick their managers is any sort of test as to whether the person can manage. People sometimes become the boss without any sort of training as to how to manage people. Of course, that's not always true, but oftentimes someone becomes a manager without having significant experience in being in charge of people.
Even without training, it's possible to avoid being a bad boss. Wanting to be better and to do right by your employees is, in fact, an important piece of the puzzle.
One size does not fit all
There are jobs where a certain amount of rigidity is required. Sometimes a missing person or an exception to the rule can throw off the work of everyone else. In most cases, however, that's not true.
Listen to your employees and be flexible when possible. Perhaps someone is willing to take a weekend shift if he or she can leave early one weekday. Maybe two other people want to switch shifts because it makes their lives easier.
You won't always be able to say yes, but you should always listen and be fair. Don't play favorites, but try to work with everyone on any reasonable request.
Don't be above anything
When I was a kid, my grandfather owned a very successful company with hundreds of employees. He was the unquestioned boss and was well respected, partly because no task was beneath him.
If a phone was ringing as he walked by, he picked it up. When a customer needed help, he never hesitated to give it.
Even though he signed the checks and was the boss, he showed his employees that he valued their work, by being willing to do it too. It wasn't a calculated move; it was just his nature. But it made people want to work for him.
Admit when you're wrong
As a manager, you sometimes have to make decisions or decide when employees want to do different things. Hopefully, you'll be right more often than you're wrong, but when you're wrong, say so.
If someone else had a better idea that you chose not to follow, credit that person. And when you simply made a poor call, take responsibility and undergo any consequences an employee would face in the same situation.
Sometimes a lot -- maybe even the success of the company -- falls on the boss' shoulders. That can make it hard to make a decision that may affect people's livelihoods. It's OK to be thoughtful and make well-informed choices (in fact, that's the right thing to do) but there's a fine line between being careful and inertia.
Make your best choice, and know that you won't always be right. That goes for little things as well as big. Don't be the person who slows everyone down because you can't make a decision. Take your best shot and deal with the consequences as they come.
Caring plays a part
Wanting to be a good manager and being willing to work at it will help you become better at being a boss. Bad bosses don't spend a lot of time caring about how people perceive them, or, in rare cases, they are oblivious to the fact that they don't treat people well.
If you're in charge, remember what it's like to not be. Act in the way you wish your managers had, and remember that employees are people with lives that consist of more than work. Most employees will accept a caring boss who makes mistakes and generally tries to make the work environment the best it can be.