When I took up running initially, I placed a lot of importance in the pre and post run stretch. These were muscles that weren't used to moving at pace therefore they had to be looked after. As time went on, however, just to do the run was enough for me, spending time stretching never crossed my mind - and this was a mistake. Back, hip and other aches and pains followed and all because I couldn't be bothered with that extra ten minutes just to stretch!
This training programme has taught the importance of these stretches as an ache and pain that's not catered for by stretching now can result in a trip to the physio (or worse chiropractor) later!
It's quite common to experience tight calf muscles which can lead to other injuries (in my case the dreaded planter fascitis!) so stretching and strengthening these muscles as demonstrated in the link below is advisable.
The hamstrings can also cause bother for long distance runners so the exercise below may help you overcome any hamstring problems you may have.
Before you warm up if may also be worthwhile doing a few exercises like the ones below
After the run these quick cool down exercises may also help
Throughout your programme, you will undoubtedly feel knocks and strains and it may also be advisable to see your physio for a massage to counter act any long term problems which may occur if you continue to run high mileage and at high intensity.
Remember it's all about getting to that start line in the best possible shape to enable you to give it your best shot on the big day!