There is no single approach, as there is no single problem, or difficulty that you likely face. However, there are some general rules or suggestions that make sense to abide by when dealing with a difficult employee.
Your number one priority is communication. Talk to the employee and try to understand the cause of the problem and you might just find an easy solution. Someone who comes across as difficult might be experiencing social problems with other employees that could be solved with mediation. They might feel ill-equipped to do their job, in which case some extra training or supervision might help. Whether they have a legitimate grievance, a personal crisis or just low self-esteem, the mere act of talking to the employee can help them to feel better understood, and can help you both to identify a solution. At the very least, it will enable you to move on to tougher measures, confident that you’ve done all you can.
Next, give them clear, honest feedback about what’s going wrong. Think about the information they will need in order to correct their behaviour, and make sure you’re consistent. Avoid ignoring poor performance one day, then criticizing it the next. Be clear about what the consequences will be if the situation does not improve. Avoid criticizing them personally, but instead try to remain positive: focus on what actions could be taken to reach a solution.
3. Keep records
Throughout these steps, make sure you keep careful records of every communication. Only in a minority of cases will you need to dismiss someone, but when this happens you will be expected to justify your decision. Being able to demonstrate your efforts to resolve the situation will be essential.