Know your limits
It's easy to get injured; anyone can do it. Just run too much. Your threshold could be at 10 miles a week, or 100, but once you exceed it, you get injured. Various studies have identified injury thresholds at 11, 25, and 40 miles per week. Your threshold is waiting for you to discover it.
The body needs time to adapt from training changes and jumps in mileage or intensity. Muscles and joints need recovery time in order to handle more training demands. If you rush that process, you could break down rather than build up. Be the tortoise, not the hare. Increase your weekly and monthly running totals gradually. Use the 10 per cent rule as a general guideline, but realise that it might be too aggressive for you - especially if you are injury prone. A five per cent or three per cent increase might be more appropriate.
Keeping a detailed training log can help you gauge your personal training threshold. Record your weekly mileage and how you feel after your runs. Look for patterns. For instance, you may notice that your knees ache only when you're logging more than 40 miles a week.
Listen to your body
This is perhaps the oldest and most widely repeated advice for avoiding injuries, and still the best: if you don't run through pain, you can nip injuries in the bud. Most running injuries don't erupt from nowhere and blindside you. They produce signals - aches, soreness, persistent pain - but it's up to you to not dismiss them.
Use Strength Training To Balance Your Body
You need something to keep your body properly aligned while you're running down the road at 200kg of crunching, twisting-in, and torquing-out force per stride - and what better than muscle? Strengthening the hips is optimal for effective rehabilitation, as opposed to treating the area where the pain is located (e.g. your knee). When you strengthen the hips - the abductors, adductors and gluteus maximus - you increase your leg stability all the way down to the ankle.
Healthy running should be as symmetrical and fluid as possible. If you don't have muscle balance, then you lose the symmetry, and that's when you start having problems.