So you want to use lag to win the game or lag to frustrate the cheater?
Use the lag cheat.
Remember you can only use lag when you're hosting the game.
So you need to know when you are the host, which is not that difficult.
Blue host is the host of the first half, red host is the host of the second half.
When you are in extra time the red host stays the host of the first half of this extra time
and the blue host will host the second half of this extra time.
Now that we have cleared that up we need to use lag in our half.
You need to upload some data/file at maximum speed.
In essence you want to maximize/saturate your upload using some programs.
The opponent will have a hard time to get the ball and you can score goals and win the game.
Different programs can be used to accomplish this:
Emule/utorrent: any p2p program will do as long as you can seed at maximum upload speed
MSN/FTP/upload sites: you want to upload a large file to somewhere at full upload speed.