what type of internet service do you have? also what brand router? i just went trough this a couple weeks ago..so it's still kinda fresh in my mind...you have to log into your router, and set ur security settings to minimum, this allowing incoming and outgoing data to be allowed freely....for some reason when i put my settings on normal, with the correct ports forwarded it doesn't show up on the public server listing...so i just switch them back when i am done with my session....but anyway...log into your router and forward ports "any -> 27015" that allows the incoming/outgoing data to be recognized as "ok" i guess and everything should be good to go...some routers even have "preset" options for port forwarding based on what game u are playing...mine had a "half-life server" option with was extremely convenient...any questions please feel free to ask and i will try to walk u through as best i can..