First tip. Your feet these are the things that are going to be carrying you through this, so they need to be looked after, keep them clean make sure that your toenails are trimmed.
Make sure your trainers fit well and are comfortable a few runners say it is best to try new trainers on later in the day when your feet are hot, this is your call but always make sure you only wear them on short runs to begin with, you do not want to be wearing new trainers on the day of a big run, they need to be already be worn in, or you may get blisters on the day ,but we don’t need to encourage them.
What about the socks ? make sure you turn them inside out and check for loose threads before the day of a big run, make sure they fit comfortably don’t have them to tight, socks can do a lot of damage if they cut into you.
Now the exercises for the feet while sitting in a chair. You need a tennis ball put it under the arch of the foot and roll it down to the ball of the foot then up to the heel this will help to stretch those muscle in that area you also need to grip the toes in and out a few times a day again to stretch muscles in the foot, also again while sitting a form calf raises this will help the Achilles tendon.
You also need to pamper your feet, massage between the toes around the toenails under the toes, you can get cracks in the skin there and don’t forget the ankle ( always massage towards the ankle then up towards the lower leg with firm but gentle pressure you can always use a bit of olive oil ) look after them tootsies now and they will do you proud on the day.