For a first attempt, use aireplay-ng -3 instead of the -2 attack...this replays ARP packets. Once everything is setup (airemon-ng listening and aireplay-ng running), you'll find an ARP packet faster if you disconnect and reconnect your other laptop on the network. There are methods for doing all this without clients. For that you'll have to do more reading. You can find nearly everything you need on the forums and here:
http://www.aircrack-ng.org/doku.php


