You might go to an "Intro to DBD" at a festival to get started.

But never fear. If you can't do that, it's not too late. Basically, you can just start dancing DBD. It’s not like moving from Mainstream to Plus. There is no separate defined list for DBD. You already know (or should know) all the moves. It’s simply a matter of using them in new ways. Most DBD groups effectively operate as workshops, and welcome solid Plus dancers. The callers come to the dance with choreography in mind; ready, willing, even anxious to explain and demonstrate the things that cause the dancers difficulty.

I'd also like to mention that Four County Squares Workshop in Carroll County Maryland is specially devoted to helping bring plus dancers into DBD.

There are some rules of thumb that might help.

• If told to trade, do a partner trade or regular trade.
• If told to Circulate, ignore anyone else -- just pay attention to where you are and do the call. You may pass someone, for example (ex. two facing lines, told to Circulate, essentially are just doing a Pass Through!)
• Callers like to do things like "do the centers' part of Load the Boat". Remember, Load the Boat starts with a Pass Through. OK so far. Then, it does a "quarter out" (Taminations says: turn your backs to your momentary partners). Note well, you may be turning the opposite direction than you usually do! Then, Trade and Pass Thru.
• Relay the Deuce is another common thing used in plus DBD. For standard-position plus dancers, its going to feel peculiar. Guys in particular -- you may find yourself heading back down the central chain the "wrong" way for a bit at the end, and in standard-positioning you've never done that before!