Interval training is fantastic for improving your fitness and stamina. This form of interval training starts with you doing the longer interval to really push your limits. It then reduces down in time, but speed increases and then goes back again (this example goes for a total of 35 mins). It sounds fairly brutal, but it gets the heart working really efficiently and you’ll get that great lactic acid burn!
Caveat: try this once you’re used to running as I wouldn’t advise it for your first introduction to running! Check out my other post on starting out