If you're like most organizations you ask your managers to assign a rating to employees during the performance review process. No one likes to be rated and most people don't like assigning ratings. Read a blog post we've written on ratings for more in depth exploration on this often debated topic.
Now back to the fact that you may need to have a rating system. Because we promote the fact that what is achieved in the job is just as important as how it's acheived we suggest considering a system that simetaneously rates both Job Competence (job responsibilities, skills and goal achievement) AND Behaviors.
The advantage of using a dual rating system is that it can more accurately reflect the actual performance contributions of the individual being rated. Case in point: the highly competent employee who accomplishes all of their job responsibilities yet treats their colleagues like second class citizens. In otherwords, the work gets done but their behavior towards co-workers is deplorable. On a rating scale of 1 - 5, five being the highest, the manager might be apt to give the employee a 4. Discounting the rating by one point to account for the employee's lousy treatment of colleauges. In reality the Job Competence really is a 5, the highest rating and the Behavior rating should be a 1 or 2 at most. Click here for this example.
A note about on-line tool ratings: In some online employee performance management systems, you are able to weight each competency or performance goal based on priority giving you the flexibility to choose the best rating scheme, and even mix and match rating scales by form, based on the position. Here's a worthwhile article originating from Halogen Software on how to choose the best rating approach Choosing the Best Method to Assess and Rate Competencies.