Wireless "Look Mom: no hands!" 
Today, most Macs have a wireless network card build-in. Otherwise, it's easy to add one; you only need to put in a so-called 'Airport Card' (made by Apple or third party manufacturer).
Every Mac is prepared for WiFi; it already has an antenna inside.
Note: WiFi' means 'Wireless Fidelity'. With your Mac, which is WiFi certified, you can connect to any wireless network in the world.
Do I need to install additional software?
No specific software has to be installed. Mac OS X will recognize the Airport card and display its settings in System Preferences => Network, just like with a modem or ethernet connection. However, it is wise to check if there are any software-updates after installing an Airport card.
Security
There are some things you should know first before connecting to or establishing a wireless network.
To prevent others to read the data that's being send through the air with radio signals, there are several security protocols available. The Mac can connect with WEP and WPA secure connections.
Note: WEP isn't very secure anymore. It can be hacked in minutes.
Why security, the Mac is a secure system, isn't it?
WiFi is a radio connection. Anyone with a suitable receiver can receive these radio waves and download the information that is being send. That means also your credit card number and bank account data. So this is why you'll need to encrypt the data to prevent others from reading it. The encrypt and decrypting software comes with your Mac. You only need to choose some passwords.
An encrypted WiFi network
To connect to an encrypted WiFi network you need to know the following things:
- the kind of encrypting protocol that's being used
- the password to the network, called a 'key' => WEP key or WPA key
A closed WiFi network
Every network has a name. In a closed WiFi network the name, SSID (Service Set Identifier) is not being send. To connect to a network like that, you 'll need to know the network's name. In other words: the SSID-code.
You can log on to a wireless network in case that:
1. your Mac's equipped with an airport card
2. your Mac's within reach of the WiFi base station***
3. you know the kind of encryption (if there is any), password and the name of the network (in case the network is a closed one)
Connecting to an open, non-encrypted wireless network
Go to System Preferences => Network. Keep 'Location' on 'Automatic and choose at Show Network Status: 'Airport':
The Airport status is shown. In most cases, you are already connected by now, otherwise select the open network from the selection of network names. Choose the one with security 'none':
A second possibility is to choose "Show Airport Status in Menu Bar". Now you can go to your Menu Bar and select the network you want to connect to:
Connection quality
The little wireless icon in the Menu Bar shows the quality of the network. When all rays are black: the connection is excellent, when (all) most rays are gray, the connection is (very) bad. Connection quality can be influenced by:
- distance to the wireless modem/router
- obstacles like reinforced concrete, piping, microwaves, water-tanks etc
- an other wireless network at the same radio channel
- anything that can act like a Faraday Cage
WARNING
Connecting to an open, non-secured WiFi network is quite easy. However, an open network is not secure. So, beware not to use it to send confidential data, for example credit card numbers, passwords.
Connection information
At the Network panel you can see your IP address and the IP address of your Wireless router:
Connecting to a closed, encrypted wireless network
Go to the Menu Bar and click the Airport Icon. Choose, if possible, the network you want to log on to. Isn't the network visible, choose 'Other...'.
A window appears in which you can fill out the log on information you got from your system administrator:
Isn't the network's name appearing in the Menu? Choose 'Other..' and insert the network's name and log on information.
An alternative way to configure your Mac for a wireless network
Open the 'Internet Connect' program and select or create a network:
Configuring an Airport or Airport Express base-station.
For this, we use the Airport Setup Assistant program, which we find in Applications/Utilities:
You can also use this program to change* the configuration of an existing base station:
* Off course you need its password
Airport
Name your base-station and your wireless network here. Next thing to do is to choose the encryption at 'Change wireless security':
Wireless security options:
For security reasons, you can also choose 'Create a closed network', so the network's name won't be broadcasted.
Note: Remember to configure the security at the highest level possible. In case you have some older computers with only WEP capability, choose WEP (64 or 128 bit). Otherwise choose WPA personal.
Configuring a third party WiFi router or modem.
Most routers and modems can be configured with their build-in web-pages.
First, connect your Mac to the modem by wire. Then, type the modem's IP address into your browser to log on. The manufacturer has that information and also log-on information for you. Remember to change the default password of your modem/router!
Connect the base station to WAN or LAN
In case your Airport base-station is connected to a modem or router. Usually, "Configure though DHCP" will do the trick (default). Imagine your base-station is just another Mac hanging on a modem/router:
TIP
Manual ethernet configuration
Share random or fixed IP addresses?
You can configure how the Base-station runs it's network. Does it have to give all computers a random IP number? Or do you want to give every p.c. a unique IP address?
Just click "..... IP addresses" to let the Base-station give IP addresses automatically on a random base.
Secure by using the Mac addresses
You can also choose to let the Base-station recognize a unique computer by the MAC address** of it's WiFi card and give it a certain IP address. This is another security measure: to only let certain computers use the network:
A MAC address** is the unique hardware number of your network card. To find the MAC address, go to the Apple Menu => 'About this Mac' => 'More info...':
=> 
Port mapping:
The Airport base-station has a Firewall on board. It can be necessary to open some ports and let the data pass through. This is called port mapping:
WDS
Use an airport as Wireless Distribution Service: enlarge an existing WiFi network
Bluetooth 
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