In the past I've been adding 1/2 mile per week to my mid-week and weekend runs. My goal was to get those runs up to 10 and 15 miles, respectively. My first-of-week run is capped at 5 miles as a rest run. I've been careful to listen to my body and to modify my runs accordingly, reducing the distance, skipping a run, etc. This listening to my body has been a short-term effort. Short time being the immediate future, i.e. that day.
I've been discussing my injury last year with a running friend named Boscho who is also a medical doctor. He has helped me realize that in addition to focusing on the short term, I need to focus on the long term effects of my running. Long term means that I understand how my running today may affect my body days or weeks in the future. The reason this is important is that running causes stress on my body, and if I advance in distance or speed too quickly, the stress can build up over time until an injury occurs. Stress today might injury me in 2 or 3 months.
Boscho thinks (and I agree with him) that this is why I was injured last fall. For six months prior to the injury I had focused on running a faster LSD pace, and my LSD pace had gone from about 11:30 to 10:15 to 10:30. After the six months, I stopped increasing my pace and immediately began to increase my distance. Think about this: I increased my pace over a six month period, and that put a lot of stress on my body. With my body under that stress I began to increase my distance while running the faster pace, and after about 2 or 3 weeks of increased distance, I was injured. What I should have done was stop increasing my pace and then run the faster pace over the distance I'd been running for enough days or weeks that my body had gotten used to it, that is, until my body had adapted to the higher stress. Then, I could start to increase my distance and have less risk because my body was used to the higher pace.
So, I'm changing my training such that I will allow more time at each increase in distance before I increase again. Five years ago I trained this way. I would increase my distance and then run the new distance for 2 or 3 weeks until I felt energetic. I started to make weekly changes after my auto accident in May 2004. My body seemed strong, and I made weekly changes in distance and did OK. But, I'm older than I was 20 years ago, and I need more time to adjust to stress. My new change to my training means that instead of adding 1/2 mile each week, I will add 1/2 mile every two weeks at the minimum, and I may go three or four weeks before I increase again.