If something is written down as a goal or comment on your review, ask why. Ensure that the details of the review process are clear to you so you understand what is expected of you for the year and you can work toward goals or make corrections in how you are working.
Make sure you understand the reasons why you are being given a certain rating. If you decide to challenge a specific rating or your overall rating you will need to know the reasons why your performance was rated the way it was.