Before I get into some tips for network and Internet setup (using the Network and Internet panes of System Preferences), I want to briefly discuss networks and network ports in Mac OS X, because many users confuse the two.
A network is a group of devices connected in a way that allows them to exchange data with each other. A network can be as simple as a laptop, desktop, and printer in your home, or as complex as millions of computers located all over the world (which is what the Internet really is). Some networks are public (the Internet), whereas others are private (a LAN at your office). Generally speaking, if two or more computing devices are communicating, they are doing so over some kind of a network.
A network port in Mac OS X refers to the type of connection your computer uses to connect to a network: Ethernet, modem, AirPort/802.11 (wireless), Bluetooth, etc. Even FireWire can be used for networking, although at the time of this writing such networks are rare.
It's important to know the difference between these terms, and to understand that there is no inherent link between them. For example, you could use Ethernet to connect to the Internet, but use AirPort to connect to other computers in your office or home. Or you could use AirPort to connect to other computers (and even printers connected to those computers), but use your Mac's built-in modem for dial-up Internet access. In our home, our iBook uses AirPort to connect to the Internet and our desktop Mac, but Bluetooth to send files to a friend's laptop and our wireless phone.
Now that I've got that out of the way, let's talk about the various network- and Internet-related settings.