Schools have different appeal procedures. Be sure to check with the school you applied to ensure you follow their process.
In general, a college will not consider an appeal unless you provide new information.
The student needs to write a letter stating why they should be reconsidered. In the letter, which should be mailed, include one or two new letters of recommendation, an updated transcript and any other new information such as awards won or special circumstances.
Be sure to act quickly, some schools have a short window of opportunity for appeals.
It is important to correspond with the college soon after you receive a rejection letter. It shows your interest in the college and they may only have a few slots for appeals.
Being persistent may pay off.