If you are one of those unfortunate souls that are struggling with LAG in WoW and other MMO games there are a few things you might want to do to hopefully decrease this issue.
First thing you want to do is do the Registry Fix and this is how:
2)Browse to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\Tcpip\Parameters\Interfaces
3) Browse the items under interfaces until you find one that has an IPAddress entry matching the network interface you want to affect (typically LAN IP addresses start with 192.168 or 10.0); note that if your IP address is automatically assigned by a DHCP server you may need to look for a matching DhcpIPAddress instead of IPAddress
4) Right-click on the interface and select New > DWORD (32-bit) Value, name it “TcpAckFrequency”
5) Right-click the new TcpAckFrequency value and select Modify, enter “1″ (Hexadecimal radio button should be selected)
6) Right-click on the interface and select New > DWORD (32-bit) Value, name it “TCPNoDelay” (note that TCP is all uppercase this time – that’s intentional)
7) Right-click the new TCPNoDelay value and select Modify, enter “1″ (Hexadecimal radio button should be selected)
8) Verify that both TcpAckFrequency and TCPNoDelay now show up in the adapter’s property list with types REG_DWORD and values 0×00000001
9) Exit regedit and reboot (reboot is necessary for the changes to take effect!)
10) Play a game and enjoy your new low ping
If you are not sure how to do this, or choose not to do it manually then there is a workaround as well. Download Leatrix Latency Fix which is basically a script that will do the things that are explained above.
If you have done these things and you are still having issues with your latency, then you might have an issue with your ISP and it would be a good idea to call them up and ask them what gives. Now the last scenario is where you are getting a crappy lag issues due to the distance of your place to the servers. Even if this is the case there is a way to combat this, but it will actually cost you.
What i am talking about is using a service as Smooth Ping or Battleping which can prove to be very useful and lower your ping from 400 to 80ms. With Smooth Ping and Battleping you can download it and try it out for free before decide if you like it or not, and buy it or don't buy it.
As for basic setup this should prove effective in lowering your ping, but if other means and ways arise and i hear about them i will share them here.