Presuming you're running it on a closed network for people on other site networks, you'll need to be sure you can get ports opened that your other players can connect on. I suspect network security is too tight, and furthermore, you won't have access to the routers to set up a port forwarding.
IF, however, you're a guy with access to those routers, or such a guy owes you a big favor, you might be in luck. You can use the server.properties file in the server folder to set up which port your guy on the inside opens for you.
If you're running it on a LAN, though, or even just a large intranet, you might not have ports screened at the layers your players will connect from. Again, check the server.properties file and change the ports until someone can see you on your IP. For info on how to find your IP, see the IT guy who owes you a smaller favor, or is maybe just lower rank than you.
Also, there's an option in server.properties for disabling Mojang username verification; use it.