Understand that positive reinforcement involves much more than giving a pat on the back or designating an employee of the month. It's a powerful interpersonal tool that must be used carefully. Make it personal. No one reinforcer works with everyone, so find out what each person values. Make it earned.
People respect most what they earn.
It's your job to set up opportunities for people to earn positive reinforcement. Make it immediate. When you see desirable behavior, reinforce it immediately. The more immediate the reinforcement, the more effective it is. Try to catch people in the act of doing what you want.