Aim for three days running a week. It is preferable to run on every other day in order that you allow sufficient time for recovery.
Runners: 4 X 5 minutes easy running with 2 minutes walk between each.
Run at a pace that you could talk at. Repeat this session three times taking care to warm-up, stretch, run, and then stretch after the run.
Walkers: Three sessions of 30 minutes brisk walking on alternating days to allow recovery.