Advantages in using a flight sim to prep for a private license? I'm starting to save up to get my pilots license and I was thinking I might be able to do some amount of prep work by using a flight simulator.  That being said, I realize there must be some huge limitations to what I can actually learn, on my own, on a flight sim.

So, out of curiosity, are there good things to try practicing on my own in a flight sim?  There's got to be a few basic things that would make it worth my time...  Otherwise I'll just go back to flying around aimlessly like I usually do :).
I'd advise against "flying around aimlessly".

Even if it is a simple, routine flight between two nearby airports, fly it fully, and try to fly it as professionally as possible (can you keep your heading to within +/- 3 degrees? can you keep your altitude spot-on?)

Another good exercise is to do all your navigation planning in detail (each heading for a certain number of minutes), then try to take off, and using nothing but the compass and stopwatch, find out how close you get.  (and when you end up off-course, figure out where you went wrong!)