To get started, I simply switched OSX into dvorak mode in the International preferences panel and then turned on the keyboard viewer to see the layout on screen. I started just doing things like facebook messages, and it was painful. Minutes just to type a few sentences. But within a day it seems reasonable to be up to 15 wpm or so.
The main thing for me was only using it for social communication or typing games, which allows it to remain a fun challenge rather than a big frustration.
I still use qwerty often for dev-related things because the muscle memory for shortcut keys seems harder to overcome than it was for typing words.
I then spent some time each day practicing related words. This helped to bed down a memory of where the keys were and then to build up muscle memory of the combinations. A typical practice could include 'there then that thin thine ten hen her this' etc. This helped to focus on the keystrokes/combinations on a subset of letters.
This works for any keyboard layout - I used the same approach to move from my original hodgepodge approach to QWERTY.
I was looking into trying Dvorak a few years ago, and was talking to a friend that used it for a few years. He liked it, said it was a little bit faster for him than QWERTY.
The reason he switched back is because with multiple devices, very few able to use Dvorak, the benefit of being used to using a single common standard (he felt) far out weighted any benefit he got from using Dvorak while on his PC.
This is what turned me away from using Dvorak. Doesn't answer your question, but I thought it might be good to have another opinion here.
There's no point using it on the iPhone for example as you're using two thumbs. I suppose the iPad might count since it can use external keyboards but if they're going to support qwerty and azerty etc. it wouldn't be crazy to support dvorak too?
http://www.tuaw.com/2010/03/19/ipad-dvorak-hardware-keyboard...
There's plenty of typing tutors for all platforms, a surprising number support Dvorak and working through their graded lessons will get the common keys memorized in no time.
A print out, open window or desktop background with the key layout will get you through the early stages.
I forgot to ask if it has increased your WPM and by how much if it has.