Everytime someone says that, then asks, "how do I start?" I always answer the same thing:
Couch 2 5K
That is the best program to start on the path to become a runner. Why is this program the best? Because it starts you SLOWLY and is FLEXIBLE. Some people can cruise through the first two weeks, get stuck on week three, and may need to repeat it. No problem. Other people need to take the 8 week program and make it 16 weeks. No problem. It is such a smart, no nonsense program.
Also, not to be obvious, here, but, it's a PROGRAM. I feel that new runners (okay, and even experienced runners...) need something to STICK TO. Something to be accountable for. And this program is just that.
So, if you want to become a runner....get your shoes, start the program, and sign up for a 5k (about 8-10 weeks after you start C25K). By investing the $ you'll commit yourself to the program. And, once you run your first 5K, it's over. You're an addict!