What is the method used to evaluate employee’s job performance?

There are different practices done by different HR professionals. Best in my sight is to create non-influencial/un favored  balanced KPI score. For that proper JOB Analysis has to be done and deliverable has to be created and communicated to each. Based on those deliverable scoring can be done in a way that should be influence by manager's favouritisim.

Leader evaluation;Past Now and future employee plans to uncrease sales or decrease expenditure.based on employee committment.