In case your wireless card is not automatically detected, you must download and install the driver manually. Plug in your laptop via ethernet (as the wireless probably doesn't work) and install this package:
For 10.04 install linux-backports-modules-wireless-lucid-generic
For 10.10 install linux-backports-modules-wireless-maverick-generic
Restart Your Computer
Once your computer is up and running, double check that your card is recognized by right clicking on the wireless icon on the right of the top taskbar.