You should include the achievements that make you feel particularly proud or that help to demonstrate your talents and interests. Keep in mind that a judiciously selected sampling may make a stronger impression than an exhaustive list.
For academic awards, please include enough detail so that we will understand the context of your accomplishment. For example, if you have won a poetry contest or been recognized in a math competition, let us know in general terms the number of entrants or competitors and whether your award is an individual or a team achievement. You would not need to provide descriptions for common extracurricular recognitions, such as first chair of the orchestra, science club officer, sports team captain or yearbook editor, but do note your title or role. If the activity or achievement would be less familiar to those outside your community, you may wish to include a brief explanation.