• I need a three week lead time to write recomendation letters. 
• If, two weeks after I agree to write a letter of reccomendation for you, I haven't e-mailed you to say that I've written the letter and sent it off, you should send me a (gentle) reminder. 
• If you will be providing application information to which ever program/employer you are applying to (such as essays, resume, transcripts, etc.), it will be helpful to me if you provide me with (draft/unofficial) copies of that infomation when you ask for the recommendation.  The idea is that such information might (a) jog my memory and (b) help me think of good things to mention or emphasize. 
• Also, if you have any suggestions of the type of information that you would like me to write about or that the person (or people) reading the reccomendation letter would like to read about, you should let me know -- that's also good information for me to have.