When I was younger I did an awful lot of running. I competed at schoolboy level at 800, 1500 and 3,000 metres and I also did the Bolton Marathon in 82.
One of my goals was always to run a mile and a half in under 8 minutes. I eventually achieved a time of 7 minutes 58 seconds at 31 years of age.
If anyone wants to get seriously fit then the mile and a half test is a great way to do it. It's the optimum distance for cardio vascular activity. A fit person should be able to run a mile and a half in under 10 minutes but for an average person it takes around 15 minutes.
If you have the time then just work out a route from your home and back which is exactly one and a half miles. On your first run don't push it. Take it nice and easy and at the end make a note of your time. Try it the next day and see if you have improved. By the end of the first week you will surprised at how much you have shaved off your initial time. By the end of the month you will be looking at the 10 minute mark and once you have achieved the magic under 10 minute time, you will want to break the 8 minute barrier.
If you can spare 20 minutes a day and are prepared to dedicate yourself to the task then you will be amazed at how much progress you will make.
The important thing to remember is that the distance must be one and a half miles and don't push yourself too hard in the first week. Every small gain is a bonus.
Remember, being fit is not about how fast you can run, it's about how quickly you recover from physical exertion.
Don't expect to run under 10 minutes if you are overweight. I was only eleven and a half stone when I achieved my lifetime best and I stopped running after that.