Hi there,
Before you plan for improving performance you need to identify what is the gap in the performance so you can do the necessary to close gap between the required and available.
Once you identified your gap you need to choose your method of performance improvement, either by training, internal, external, job enragement, on job training, job rotation.
There fore please do review your performance appraisal system your using. On the other hand do use the search to find more on this cite on gap analysis
Regards