The first step in securing your wireless network is the same as the first step for just about everything else in computers and computer networking -- always change the defaults. Any attacker can find out what the default username and password is for a given program or device in just a few minutes. The defaults may be great for letting you connect and get the device or program up and running quickly, but in order to keep snoopers or would-be attackers out, you must change the defaults as soon as possible.
Often, the default settings are so common that an attacker doesn't even need to do any research. Many vendors use Admin or Administrator as the username and something like "admin" or "password" as the password. A couple of "educated guesses" and an attacker could infiltrate your wireless router or access point.
Refer to the owner's manual for your particular device to learn how to access the administration and configuration screen, and change the default password as soon as you set the device set up. You can also check out our step-by-step instructions changing the default password on a network router. We also have guidance on how to choose a good, secure password.
Some vendors don't provide a means for changing the username, but if it is possible you should also change the default username. Knowing the username gives an attacker half of the information they need to gain access so leaving it set to the default is a security concern. If you can change it, make it something that won't be easily guessed. Don't use Admin or Administrator and avoid using simple usernames like your own first or last name.