a) Use your router's GUI to look at association status or a connection log to verify that your client is actually associating to your router. You can also see association status on your client, either by looking at the wireless card's client GUI or by looking at the Network Connections control panel status. If your client is not associating at all, then you may have a basic mismatch in wireless parameters. Check SSID and channel (if configurable).
b) You do not say what security settings you have in place on your wireless router, but if you are using 802.1X or WPA, then your client could be associating correctly but then failing authentication. Try getting the connection to work without security first by setting both the router and the card to use no encryption and open (no) authentication. If this is fixes your problem, then work on getting the right matching security settings on both devices.
c) Next, look at the client's connection status panel. Click on the support tab and look at the IP address. If the address is either zero or "169.254.x.x" (the automatic range used when DHCP fails), then you are not getting an IP address from your router. Look at your client's TCP properties to verify that it is using DHCP to get its address automatically. Then check the router's configuration to make sure that the DHCP server is enabled. If you make changes to either side, reboot your router, then your PC, to make sure that the wireless card (re)issues a DHCP request after the router's DHCP server is running.
This was first published in November 2003