That was me, I got very lucky landing the place at JAW so early. I basically started shaping my folio back in January and wanted some opinions on it, and it pretty much went from there.
I think apply when your portfolio is to a good standard, pretty much a repeat of what PixelMasher said.
But it doesn't hurt to network and get talking to people in industry before then.
Just chip away at getting some badass work on your folio while being critical of what you want to show, take critique on it from everyone you can to create a seamless example of your capabilities.
Good luck dude! ;)