What are the important tips that helps to deal with diffficult employees?

Dealing with difficult employees depends upon the situation and why and how they are perceived as difficult. Best approach is to sit down with them privately and discuss your specific perceptions, give them a chance to think and respond (they may not perceive themselves to be difficult) and agree on what needs to change for them to continue in the organization. Leaving the situation unaddressed is a big mistake and hoping it will go away without intervention does not happen.