Excellent advice from Matt as usual.

The memories of stressing out over the grad school letters are still vivid after some 8 years. But I did my homework (research with two of the letter writers and TA-ship with the other), and it paid off.

I do remember one episode when a recommendation letter was due at midnight, and I've been emailing reminders to this professor up to the hour the submission was due. He eventually replied saying that his plane was late, and he wouldn't be able to submit until 1am.

It was for a national science foundation fellowship, which I got, so I suppose the late submission was accepted in the end. Fun times.