This video demostration using AirCrack suite to show us how easy we can send a deauthentication packet to a client so we cause him to connect again and thus giving us his WPA-PSK key. After we get they key the only thing left is to crack the key, either by bruteforcing or dictionary attack (hybrid). It would be a good way to precompute the attack using rainbow tables but you will have to build the rainbow tables based on specific SSIDs. You can see a video demostration of how simple you can get the key from WPA-PSK connected clients. Depending on the key length it will take more time to be break if you are using a bruteforce method. There are lot type of attacks nowadays.