When should I ask a prof for recs?

<p>Hi,
I was just wondering when to ask my profs for recs? Im kinda confused about it , i wanna try NYU for fall 09 and i was wondering when would be a good time to ask my prof for recs? ( i know its a stupid question :( ) </p>

<p>Thanks!</p>

<p>have you already completed the class taught by the professor you want your rec. from? if so, do it now, no need to put it off and wait for her/him to forget about your performance in their class</p>

<p>if you are taking a class with the prof. now, i would ask at the end of the semester or at the beginning of next semester</p>