Don't Criticize Publicly
Have you ever been put down in front of other people? It feels pretty horrendous. Being berated by your boss in front of others feels just like being bullied as a kid. We teach our children not to do it, so let's not practice it ourselves. Negative reinforcement, though often depicted in popular culture as the tool of choice for coaches, bosses and other leaders, is not the most effective motivator. It can break your spirit and is proven to diminish productivity [source: Manzoni].
If you have an employee with performance issues, schedule a private meeting and give some constructive feedback. Don't do it in a public place or an office with glass walls. It's never OK to make a show of publicly scolding an employee.
Talking negatively in the open about other employees, supervisors or your company is not all right either. The old adage that what goes around comes around exists for a reason. It's pretty common to get smack talked about you when you talk smack about others. And just as your friendliness can affect the entire staff (see Rule 9), your negativity can reverberate through the office and create a poorly performing team.