Programming is very important, if you don't already have a background in it. C++ and Fortran seem to be the two I hear thrown around the most. But once you learn one language, it's pretty easy to pick up another since they're all based on the same concepts, so learning more than those two wouldn't take much and will make you more marketable. Java might be a good idea as well. Python is getting more and more popular in general, but I don't know if it is in the physics market.
I'm learning how to speed read, but that's sort of a personal thing more than a "you need to speed read to get anywhere" thing. I think it will come in handy when I start reading tons of papers a day. It helps with comprehension as well, which is the most important to me.
I would also say try to expand on your social/communication skills. I kind of feel like it might be underrepresented when people ask for the skills they need. You'll likely need to do some public speaking and explain technical details for funding, so if you think you might have issues with that, work on it now.