For me, running injury prevention is largely about three variables:
1. Number of times per week I run
2. Distance of those runs
3. Intensity (speed) of those runs
If I try to increase all three at once? Guaranteed injury. Two is the most I can do.
Intensity is the real insidious one. The majority of runs should be at a very easy pace - much easier than what many of us (raising my hand here) do/have done. For years, I did too many runs in that dead zone -- too fast for everyday runs, yet too slow to have any training benefit. As an added "bonus", running in that range makes me more likely to end up injured. These days, when I run with a watch, it's usually to make sure I'm not going too fast, as opposed to trying to run faster/keep a certain pace.
Right now, I'm getting back to ultra distances, so I'm increasing those first two variables. I'd like to run faster, but I'm gonna have to let that one go this time around (not that speed is really that big a goal for me anyway -- whatever speed I had, went away years ago). If I tried to throw speed workouts in there too, I'd be on the shelf by Memorial Day.