Although at least a month is preferable, more is better and less than two weeks is unacceptable and will likely be met with a "no" by the faculty member. The ideal time to give a letter writer, though, is anywhere from one to two months before the letter is due with your submission.
You may want to include a college essay heading with a page number and your application ID. Don't include your name unless it's specifically requested. Oftentim... more