I would consider this schedule from Runners World.
Getting started 30 min running
Week 1 Run one min, walk 90 seconds. Repeat eight times. Do three times a week.
Week 2 Run two mins, walk one min. Repeat seven times. Do three times a week.
Week 3 Run three mins walk one mins. Repeat six times. Do three times a week.
Week 4 Run five mins, walk two mins. Repeat four times. Do three times a week.
Week 5 Run eight mins, walk two mins. Repeat three times. Do three times a week.
Week 6 Run 12 mins, walk one min. Repeat three times. Do three times a week.
Week 7 Run 15 mins, walk one min, Run fifteen mins. Do three times a week
Week 8 Run 30 mins continuously.