are you only playing people with 2 or 3 bars of ping? (the bars next to their name). only people from around your area of the globe will have a low enough ping to you for a completely lag free game. If you play someone with just 1 bar then the connection between the two of you can be laggy. The possible causes of lag are:
1. distance from your opponent: if you live in the UK and you play against someone in australia, you wont get a good ping, and the half that they host will lag for you and vice versa.
2. slow connection: if you have less than a 1mbit/s connection and 256k upload speed then you might experience lag, as the data cant transfer fast enough.
3. busy connection: if youre on a network and other people are using the internet, even if they are just browsing web pages, it can still have a dramatic effect on your connection. As can things running in the background on your PC, such as MSN messenger.
4. wireless: wireless conenctions are bad for gaming and should be avoided. some people say they work fine, but they often tend to be laggy and disconnect every now and then.
5. Firewalls can slow things down, try turning them off, and forward the ports on your router.
