We all know that appraisal is a good motivator. Any reinforcer would lead to more frequent occurrences of the action, while any aversion would decrease the probability of an occurrence.
You should be looking for correct actions taken by your subordinate and then praise him. An open applaud would work well here. While praising, you must specifically recognize the behavior which is good and it must be described why it was correct. This will not only make them feel better about it, but they will also take it up as a challenge to keep being in that level.
Let us take an example of a sales person having excellent presentation skills. After a particular presentation, you observed his good skills, gave him a positive response, but for whatever may be the reason, you did not compliment him on any specific point of his skills.
Though the sales person will feel good on your positive response, but there may be probably a drop in his performance the next time, maybe because he feels that his presentation skills are either not important or not good.