Guidelines in Preparing for a Performance Appraisal:

Do it in writing. The employee will understand it better and it will provide a record.
Have the employee sign it, acknowledging that there has been a discussion.
Use the job description as a base line against which to measure performance.
Be aware of the Halo Effect of giving an employee a high rating because of an isolated incidence of good performance near the review time.
Measure what the employee does, not who or what the employee is.
Have the attitude of helping the employee reach the objectives so you can justify a good appraisal. Don’t criticize unduly.
Correct small problems in performance before they become big ones.
Establish specific goals that are mutually agreed upon. This will make your appraisal program positive.
Rate accurately according to performance. If you rate everyone the same, you will lose outstanding performers and the poor ones will not improve.
Obtain the employee’s file and study previous performance appraisals, other experience, education, history, and attendance record.