Have you picked a general focus of what you want to learn? It seems to me that it's less important which specific technologies you take classes in (for the most part) than determining which level you you like to work on. I think of it similar to programming languages: some people prefer "high-level" work, like application / UI design, or multimedia or image processing. "Low level" courses are going to be more about systems design, working with distributed / embedded systems, etc. It gets easier to choose once you've made that distinction.
You're asking about grad courses, so which CS classes have you already taken?