There are already several great posts out there that exhaustively list resources and starting points for people getting into DH (a lot of them are by Lisa Spiro, who is good at it).
This will be a shorter list. I’m still new enough at this to remember what surprised me in the early going, and there were two areas where my previous experience in the academy failed to prepare me for the fluid nature of this field.
1) I had no idea, going into this, just how active a scholarly field could be online. Things are changing rapidly — copyright lawsuits, new tools, new ideas. To find out what’s happening, I think it’s actually vital to lurk on Twitter. Before I got on Twitter, I was flying blind, and didn’t even realize it. Start by following Brett Bobley, head of the Office of Digital Humanities at the NEH. Then follow everyone else.
2) The technical aspect of the field is important — too important, in many cases, to be delegated. You need to get your hands dirty. But the technical aspect is also much less of an obstacle than I originally assumed. There’s an amazing amount of information on the web, and you can teach yourself to do almost anything in a couple of weekends.* Realizing that you can is half the battle. For a pep talk / inspiring example, try this great narrative by Tim Sherratt.
That’s it. If you want more information, see the links to Lisa Spiro and DiRT at the top of this post. Lisa is right, by the way, that the place to start is with a particular problem you want to solve. Don’t dutifully acquire skills that you think you’re supposed to have for later use. Just go solve that problem!
* ps: Technical obstacles are minor even if you want to work with “big data.” We’re at a point now where you can harvest your own big data — big, at least, by humanistic standards. Hardware limitations are not quite irrelevant, but you won’t hit them for the first year or so, though you may listen anxiously while that drive grinds much more than you’re used to …