Tips for supervisors

Recency Effect – The tendency to rate someone based on their most recent contribution, rather than their performance over the whole review period. To mitigate this bias, consider the employee's performance over the entire review period.
Central Tendency – The tendency to avoid rating at the high and low extremes and instead cluster all employees in the center. This is sometimes motivated by a supervisor’s desire to be equitable. To mitigate this bias, evaluate each employee for their individual performance.
Leniency – The tendency to use a less stringent set of standards. To mitigate this bias, remind yourself that "clear is kind" when providing feedback regarding your employee's performance and that sugarcoating the message or not addressing issues is not in the employee's best interest for succeeding in their role.
Halo Effect – The tendency to base an employee’s entire review on evaluation of a single performance objective, either positive or negative. To mitigate this bias, review and offer feedback on each of the employee's goals to ensure a more complete review of their performance over the entire review period.

Remind the employee that the goal/development review process is a collaborative effort between the supervisor and the employee that will require the employee to self-reflect on their progress and performance.
Ensure that the goal/development review captures the employee's performance over the course of the entire review period. To meet this goal, the supervisor will need to ensure they are completing documentation on the employee's performance throughout the year.
Be straightforward and honest when providing feedback to the employee to ensure that the expectations are understood.
Be as specific as possible when giving feedback and reviewing expectations. Provide examples.
Provide your employee with your written draft the day before you are scheduled to meet to review it.
Foster an environment where feedback, both positive and constructive, is normal and expected.