I'd like to add wireless to my network, and I need multiple access points to cover the whole area. I'd like to set them up so that there's only one "wireless network" that the clients see, and it switches them as seamlessly as possible between access points as they wander around (if that's not possible, then at least have it so that they don't need to set up the security by hand on each one the first time, if possible).

I've searched online, and there are quite a few sets of mixed instructions (same vs different SSID, frequency, does the security need to match exactly, etc.). Can somebody who has some experience doing this please let me know what they did? I imagine it's pretty simple, but there seems to be no clear cut "yes, you can do this" online, even though I know you can.

I have a mid-size LAN with about 20 workstations and two Domain Controllers on it. Also, I'll be doing this with consumer wireless components, if it makes a difference, not enterprise-level components (ie. Linksys rather than Cisco).