Well I would create a schedule first of all. For ex.
Day 1 - Run for 5 minutes, jog for 5 min, run for 5, jog for 5 min..
Day 2 - Run for 10 minutes, jog for 5 min, run for 10 min..
Day 3 - Run for 15 minutes, jog for 5 min, run for 15 min..
Day 4 - Run for 25 minutes, jog for 5 min..
Day 5 - Run for 30 minutes..jog for 5
Keep adding the minutes as each day passes. You want to make you body used to it. If you're a non-runner, and suddenly want to run a marathon then you need practice! Use this schedule to gain endurance, and lower body strength :)
Also, watch videos on YouTube of muscle exercises to prepare for the run.