Basically, DHCP is a four-step process.

Broadcast discovery (client), Reply (server), Request (client),
Ackowledge (server).

You can listen on the network and watch to see when these happen with
tcpdump, or you might be able to run dhclient is a verbose mode to get
some output as to what it's doing.

Basically, if you never see the Broadcast discovery step, then
something is not configured on your network settings.  I have no idea
about taking your settings from other types of OS's, but DHCP is
pretty easy to use.  Check out the man page for rc.conf.