The best way to improve on the process of the performance appraisal in your company is to reconsider the appraisal cycle and see whether you need a quarterly appraisal cycle instead of the yearly. Although it might not be the same for all teams . For example - The sales team would require a quarterly cycle as according to their KRA their targets are already set as compared to the HR team who might not have targets .
Understanding the right metrics of performance appraisal is also important to see if 360 degree feedback process provides better results or an unilateral appraoch .
Refer to this article link to get an more in-depth view of performance appraisals and what might work for you and what might not .
What should you consider for the perfect performance appraisal?