DHCP with wifi (wi0)?

I asked this in a roundabout way before, but I'll shorten it and ask again:

What is the proper way to setup DHCP for a wifi adapter? I can't find
documents for this.

From what I gather, I can't just use this line in rc.conf, because it
hasn't worked yet:

dhclient=YES dhclient_flags="wi0"

I'm guessing I need to do some sort of minimal wifi network setup first?

For instance, I do this:

wiconfig wi0 -D

I get some wireless network, let's say it's wide open for now so
authentication isn't a problem.

So then I think I set up an /etc/ifconfig.wi0 file with just this:

ssid "ssid name"

Then try getting an IP via dhcp by restarting dhclient?

Not sure, nothing has worked so far.

Any hints? I've set up DHCP servers and clients, and I've used wifi on
NetBSD on fixed IP networks. I must be missing something.

Andy