Some employees think they can get away with things because they feel indispensable, especially if it's busy.
You have to pay close attention and discipline as if it were a slower time of the year. Just as you can't make rules that only apply to some employees, you can't make rules for different times of the year. Here are some things to remember:
Have a good working environment for your employees and yourself. The best working environments are where employees know that they are all treated fairly, know what is expected of them and know what will happen if they don't follow the rules. Discipline is in place and followed.
No one is indispensable. Even your best employee can get hit by a truck tomorrow and be hurt, or worse - dead. What would happen if he or she weren't there? Everyone is replaceable, including you. You can't discipline out of fear that an employee would leave. That totally undermines your ability to keep control and a fair working environment for all of your employees.
Everyone makes mistakes. Even your best technicians and office workers make mistakes every once in a while. The best thing that can happen is that employees learn from their mistakes and they don't happen again. So always use discipline with that in mind. Discuss the situation with the employee. If he or she doesn't realize that it was a mistake, point out why and find out what that person will do not to let it happen again.
Follow the rulesYou have to enforce the rules for all of your employees. You can't enforce the rules for some and not others. If you do, those that are "favored" will know it and potentially take advantage of it. Those that are out of favor will know it too, and feel that they are getting unequal treatment. This will destroy morale at the company.
You have to catch them doing things right and say something. Employees always like compliments. And you are likely to get that behavior reinforced. This is positive discipline.
If you see something wrong, you need to say something immediately. The worst thing that you can do is to not to say anything. Employees may not realize that they did something wrong. Or they may think they got away with something and the bad behavior will be reinforced.
It's tougher to have a negative discussion than a positive one. However, you want to make sure employees know that something was done wrong and that it cannot happen again or must be corrected. Other employees are watching how you or other managers handle problems. You've got to handle the problems as quickly as you handle the positive actions.
Learn how to best communicate with your employees. Different people react differently to discussions. Some you can be very direct with. With others, you have to be more tactful. Some will take it personally. Some employees you can raise your voice to; others won't listen to a raised voice.
Discipline is tough to do. You have to be fair, but you don't always have to be nice.