I rarely follow my own advice; this means that I often have first hand experience of what my injured clients are going through.... I've had achilles tendinopathy through changing my training too rapidly and then ignoring the warning signs (pain that continues after rest and on activities other than running); sciatica through failing to keep up my hip abductor and calf strength, and I'm currently nursing forefoot pain caused by failing to notice that my footwear had worn out. A lovely mix of extrinsic and intrinsic factors! Extrinsic factors - for instance when and where you run, your footwear, your training schedule - are often easier to fix than intrinsic ones that relate to your body itself; this is where seeing a health professional, remedial personal trainer or running coach can be of great help in identifying issues and offering advice and exercises.
When I was 10 my mother took me to a podiatrist to discuss my pronounced ankle pronation that was breaking my shoes within a few months of wear. He recommended expensive shoe alterations to support my ankle; I asked if I could do that myself using the muscles and he agreed that I probably could. I figured out some exercises for myself and 32 years later I now wear out the soles of my shoes long before the heel keels over. Of course I had to take care in the initial years whilst building up my ankle strength, giving it suitable support during activities that put a lot of strain through it, and I was helped by starting young and having strong intrinsic foot muscles from wandering around barefoot. I do still have that over pronation, just in a milder form; I should therefore still be stretching the resulting tight muscles and continuing with my strength and balance training regime. Yes, indeed I should.....
As I've mentioned before, I find The Running Physio's site full of useful advice. He links to other helpful sites, and includes articles by other specialists. Here are two useful articles from his archive:
How to decide whether you should run:
Helpful tips to avoid injury:
Many of these tips will apply to sports other than running!
Tom also points out that these are generic tips; if your problem continues, then do seek specific advice for you.
I also found this site:
which has some useful information on running related injuries.