One of the things I did was do the 80/20 running plan. Basically you break your running down into EASY and HARD sessions, with 80% of your sessions being classed as EASY. An EASY run is one where you could hold a conversation as you run the whole time, HARD is exactly that, one where you put a big effort in.
The benefits are quite scientific, the EASY sessions help you to reduce the impact of muscle soreness and potential injury, whilst still gaining benefit, the HARD sessions are ones that help you to measure and make further progress forwards.
I have different types of run:
Long Run - 8k+ - Always done as an EASY session
Trail Run - 4k-8k - Always done as an EASY session and a nice break from normal running and lovely and scenic too
5k - Can be done as either an EASY or a HARD session
Cooper Test - Always done as a HARD session
Interval Training - I've got a flat bit of very quiet road where I live that has a lovely straight of almost exactly 200m. I do repetitive speed training there and back to replicate roughly a lap of the track for the fitness test. I do 7-10 reps of this with a 30 second break between each Always done as a HARD session.
Since starting it I've noticed the following:
1) Much less muscle stiffness from training and no niggles in the places where I've always had them
2) Losing weight has been easier as i'm able to train more effectively and more often
3) My HARD session times improved dramatically, even though i'm doing less of them - My Interval times are faster and have less drop off between the fastest and slowest times
4) My EASY sessions are still improving, my "cruising speed" when i'm running comfortably is much faster
5) My running form is improving, because i'm not worried about any form of time on my EASY sessions, I've been able to focus on specifics in my running style which is also having an impact.
I also do some Weight Training exercises most days, not focused on the actual weight, but focused on lighter weights with a higher set of reps. The key, whatever weight you choose is to lift until you fail, as by getting to a point where you can't complete the exercise without losing form is the zone in which you gain strength