If you are asked to write a recommendation letter, you need to discuss the subject candidly with the requester. A letter of recommendation is most effective when a person who knows the requester and his/her reputation writes it.
Another consideration is your integrity-- can you honestly write positive things about the requester? If not, you need to bow out gracefully without hurting feelings. On the other hand, if you qualify, you should brainstorm with the requester to write what he or she wishes to be said. Be sensitive to deadlines.
Reprint from "Write Express" www.writeexpress.com/recommendation.htm