For everyone that used a router to set up their 360, here's a quick (but a little complicated) guide to improve your connection.

Note: this only applies to those who: when testing their XBL connection don't get "open" for their NAT, so low, medium, strict or w/e.

go to:
http://www.portforward.com/networking/staticip-xbox360.htm
to set up a static ip

Note#2: if you fail the test for DNS,don't freak out, just put in whatever it was before (you did write it down didn't you?!?)

next go to:
http://www.portforward.com/english/routers/port_forwarding/routerindex.htm

select you're router and on the next page select "Xbox Live 360"
hope this helps, it did a lot for me

I did that a long time ago. It helped, but not much because my router's firewall was still too strict with connections. I ended up having to disable it just to play a game without lag.

I did long time ago. But its preety easy nowadays to set an internet connection for your 360

I actually STILL hadn't done this yet, thanks for the tip-off.