To start improving someone's performance, simply watch them perform their job.
Let them know that you'll be watching, and then watch. If your relationship is strong enough to share feedback, that will enhance the performance even more, but it's not necessary at first. You will likely see improved performance simply by observing.
Why do people perform better when being watched? It puts them on notice that their performance is important. It provides focus. It creates a reason to work at their best.
You might not want to do this everyday, but it's an excellent performance tool occasionally. You might even try doing the job to see where some of the process and procedure issues are. You might be surprised.
When was the last time you observed one of your team member's performance?
What are you doing to improve the performance of your team?
Who on your team would benefit from your observations?
-- Doug Smith