Problems between employees are inevitable, and if you don't have an HR department with a 60-page handbook, you are going to be the person who has to sort them out. Always be discreet, and try to deal with things in a general way first.
For example, if one employee complained that another employee was barging in on the sales floor, our first step would be to take some time at an employee meeting to go over the rules of honoring other people's sales. If the problem persisted, we would talk to the offending salesperson privately about how to behave on the sales floor. If we continued to receive complaints, we would deal with it more specifically, but we rarely have employees confront each other unless it is about deeper interpersonal issues that only they can work out.
According to research by LeadershipIQ, only 23% of employees said that their employers "respond constructively" when they share their work problems. Employees who said their employers always respond constructively were 12 times more likely to label their company as a great employer and fantastic company to work for. In other words, responding constructively to employee feedback and criticism can increase employee satisfaction.