In all seriousness: When you "go for a run" (whatever that means at your current state of fitness), insert walking breaks. These are intended to *prevent* fatigue, rather than to pay off an oxygen debt--in other words, take them before you'd "need" to.
Yeah, yeah, I know: Gallowalking! The horror! If you go out for X miles and you want to be able to say (if only to yourself) that you "ran all the way!"--then fine, do a slogging jog-trot that bears no real resemblance to your 1500m running motion. It's your running and you can do what you want.
But if you want to do some mileage that will actually have some carryover to your running action in later training or in a race:
Run for a few (or several) minutes at a normal running speed--not a hard/fast run, not a jog, just a run.
Walk for about a minute. Don't "earn" the walk by getting out of breath beforehand; again, take the walk before you'd *have* to.
Run for a few more minutes, followed by a walk. Et cetera. Repeat as needed. Finish feeling no more than Lydiard's "pleasantly tired"--not wrung out or exhausted.
Separate issue: If you're serious about this, be ready to change your sleep habits. Moving from sedentary to athletic will likely mean that you need to add a half-hour or hour to your night's sleep. In addition, make sure you're away from all screens (TV, computer, phone, Kindle) for at least a half-hour before bedtime.