Look up “performance appraisal form” in Google (with the quotation marks). You will find plenty of forms. However, I suggest you approach the problem from the other end. The performance appraisal process comes before the form. You will need to settle on your process and the objective of the process before you can even begin to decide on an effective form.
There are processes that set and measure goal attainment, some that measure behaviors as well, some that are single rater, some that are multi-rater, some that list competencies, some that list organization wide behaviors as well, some that include a numerical score, some that include written comments only, some that allow appraisee responses, some that tie the appraisal to remuneration and bonus outcomes, etc etc.
I know you want a simple form, but what is “simple” depends on the context. And a “simple” form may cause a lot of complexity further down the line as you try to fix up the damage because the “simple” form did not suit where your company is at.
Vicki Heath
http://www.businessperform.com