Summarize this article in one sentence.
Most beginners try to go too long or too hard; this is a mistake. You end up getting too sore (some soreness is normal at the beginning of any new activity) or worse, injured. If you're out of shape, and especially if you are overweight (20-plus pounds or more), start by walking 20-30 minutes, a few times a week. After a few weeks of this, start increasing your walking intervals quick walking for a minute or two, then slowly walking for a minute, and repeat. If you feel you're ready for running, or have done the above walking routine for at least a month and are ready to incorporate running, start with run-walking. That's warming up with walking for 5-10 minutes, then jogging for a minute or so, alternating with walking rest periods. If you think you can run without the walking, do it for short periods at first 10 minutes, then 12, then 15, and so on. Add some time every 2-3 runs, but don't be too quick to add the distance. And don't add faster paced running in yet. Remember that the key principle is this: your body will adapt if you give it time. Start slowly, let your body adapt to that, then gradually gradually add time. Later, when you're used to running (after a couple of months), you can add intensity. Accept that you'll be tempted to ignore this advice and be more ambitious. But don't ignore it; you'll have a much better experience with running for following it. Better yet, if you take the time to build your stamina, you will pleased with your progress and be more likely to stick with it.
Begin slowly. Increase your workout over time. Start jogging. Increase to running. Notice your increased stamina. Temper your determination.