Common biases in performance appraisals include the halo and horn effect (where an overall impression of an individual influences the assessment of their specific traits), leniency or strictness (rating everyone too high or too low), central tendency (avoiding extreme ratings and rating everyone in the middle), and primacy or recency effects (giving undue weight to performance at the start or end of the review period). To mitigate these biases, managers can use objective measures, focus on specific behaviors instead of personality traits, collect and use evidence from multiple sources and time periods, and participate in training to become aware of their own potential biases.