So is the computer you're hosting the server from going to be on a wireless connection? I wouldn't recommend doing that, if at all possible.
Are you hosting a listenserver (you make a game and play in it, it's gone when you quit), or a dedicated server? (a computer on your network hosts the game, but you cannot play using that computer) If you're making a dedicated server, there's a great site with all the information you'd need here.
Even if you're only making a listenserver, the way to get it so others can see past your router is the same. You have to forward these ports on your router. Depending on what brand of router you have, that'll be different. The website mentioned in that Steam answer should tell you exactly how to do it, if you don't already.
Then, once your server is up, make sure you give people your external IP. Forgive me if that sounds stupid, but there's far too many people who can't understand why people aren't getting in their server when they give them 192.168.0.x (their internal network IP).
And yes, there is a very simple way to host it. Open up Internet Explorer, and in the address bar, type "192.168.1.1".
Then, a box should pop up asking for a username and password. Here's what you do: Leave the username blank, and for the password, put "admin". You will now have access to your router. If you're on Linksys, go into the "Advanced" section, then go into the "Forwarding" tab. Now, type "27000" in the first box, on the left. And on the right, type "27030". Then check the "TCP" AND "UDP" boxes. Then you need to specify which computer you want these ports forwarded to, so go into Start, and click Run. In the box, type command or cmd. When the cmd pops up, type "ipconfig", then you should see a bunch of addresses. The one that says 192.168.1.x is your internal IP address, and is the one you should tell your router to forward the ports to. Now click apply in your forwarding settings, and run to host your new server.