Which is the best time to go for F1 visa interview for fall

Which is the best time to go for F1 visa interview for fall 2014.I already got an I-20.also suggest if I can apply for another university at this point of time as the university I applied earlier is costly

It’s never too early nor too late. It all boils down to the confidence you show the VISA Officer and convince him that you won’t settle down there. Add a bit of luck to it and you’re fate is sealed within 50 seconds.