The main things you're going to learn in a real world environment are hard to state in this way.
They're about working within constraints (timescales, requirements, technologies) that aren't idea and working on a scale that you won't have experienced before. University projects are at most a hand full of people part time for a few weeks or a couple of months - that simply can't compare to the compexity you'll see in a system which has had ten developers working on it full time for a year, or something that's been kicking about for five years having bits and pieces bolted on.
It terms of things you can easily state, I'd pick one or two solid technologies and say you want to work with them. Pick one core programming language you already have a grounding in (Java, C++, .NET would all be good) and one application of that (so databases, web or mobile). Personally I wouldn't start something completely new as most of what you're going to learn is not strictly technical so you don't want to have the learning curve of a language on top of that.
But other than that I'd say you want to work on something with other programmers (who you can learn from and learn how you interact with) and work with larger systems - either enhancing something that already exists or interfacing with something else.
That's the stuff university can't teach you so that's the stuff I'd try and learn on a placement.