Top-down:

The most traditional form of appraisal - manager/supervisor feeds back to subordinate based on observation, quality of work, relationship, etc.

Problems: Stresses traditional organizational hierarchies (what happens to work done outside the manager's span of control), may be very subjective (can a manager be impartial and not biased by personality differences) and is one sided (subordinate has no way to provide feedback about the performance of the manager). Can be perceived negatively by employees (us versus them mentality).

Often, an indepedant review of the appraisal takes place

Bottom-up:

Employee provides indirect feedback to manager via a rating system based on communication skills, decision making, clarify of ojectives, etc.

Problems: Can be perceived negatively by managers/supervisors (them versus us mentality).

Self:

Not used very often. Individual provides own feedback based on introspection. Can allow managers/supervisors to be mentors and counselors rather than directors and controllers.

Encourages greater ownership of responsibilities and participation in job roles.

Problems: one sided (difficult to be objective) and lenient (people often won't negatively assess themselves)