Wi-Fi Networks: One SSID for multiple access points

To setup a Multi-AP Roaming Network give all APs the same network name (SSID), the same security type (WPA2-PSK recommended), and the same wireless security passphrase. Clients usually assume that these settings will be the same across all APs with the same SSID.

Channel is one key setting you do want to vary from AP to AP in a roaming (multiple AP) 802.11 network.  You don't want transmissions to/from one AP to compete for bandwidth with transmissions to/from the other AP.

If you're only using 2.4GHz-only devices with single-band-at-a-time APs, be careful of your channel selection, as they can overlap.. Channels 1, 6, and 11 don't overlap at all, so those are good choices to pick manually. You could use a Wi-Fi network scanner like NetStumbler or iStumbler to see which channels are in use where you are.