An employee's own work appraisal is written with a professional tone and in the first person, using hard data and not hyperbole to spell out projects completed and job functions executed. The previous year's appraisal or the job description can serve as a barometer with which to measure performance.
Employees shouldn't be vague; rather, they should give specific examples, such as "I responded to calls within one hour." They should write clearly, eliminating any awkward phrasing or flowery language, and proofread so that there are no mistakes.
Additionally, employees want to focus on their career as a whole and should use the self-review as a basis of discussion about their job progression path.