How much time does my recommender need to write a good letter of recommendation?

Question: How much time does my recommender need to write a good letter of recommendation?

Answer: Faculty members are busy people and graduate admissions time falls at an especially hectic time of the year (usually the end of the fall semester). Demonstrate respect for your letter writer's time by providing him or her with plenty of advance notice. At least a month is preferable (more is better). Less than two weeks is unacceptable (and will likely be met with a "No").