Sorry, when I say WPA I mean WPA in general, no specific one. To crack a WPA2, you would need to capture 4 packets, called a 4-way handshake I beleive, and you capture these whena device is connecting to a Network, so you would force disconnect them, and then when they reconnect, capture these packets. You then brute force these packets, and then you have the password. The time in which it takes to brute froce this key, depends on how secure the password is. So always go with WPA2, and never WEP, because WEP taks 5 minutes to crack.
But anyways, my information still applies