What are the ways for delaying the onset of age related diseases?

Well, I have heard that smoking is a big thing. If you stop smoking, or never start, you have a longer life expectancy. This is kind of comical, but my sister in law said one time, I found the fountain of youth...its called NEVER GET MARRIED AND NEVER HAVE KIDS...lol...I don't know...maybe that's it...But really, a lot of things are genetic and a lot of things are not preventable, so its really hard to say!