Originally Posted by
White Mage Abyss
Wireless internet is unstable as a whole, but there are a couple of things you could do that might work.
Move closer to your wireless router, the closer you are the less the signal has to travel, obviously. If that's not an option try making sure you're not near the kitchen, or the kitchen isn't in between you and the router. Really bad wireless internet connections can be interrupted or even disconnected by a simple microwave, and if your lag is sporadic that might be what's causing it.
Get a new wireless card, Perhaps the one you have is weak and unstable, causing net lag, I used to have a laptop that would instantly disconnect if I had any other device connected to the internet.
Make sure you have no game systems that are connected to the internet on while you play, it takes up wireless signal as well.
Make sure you're not streaming anything, close all p2p connections you might have, (utorrent, limewire, ect) seems really obvious as well and I'm sure you've already tried that.
Lastly, and most importantly, make sure your wireless internet is password protected! Other people can leech your wifi and that really hurts your wireless internet.
Failing that there isn't much else you can do other than getting a new ISP or a wired connection.