2. Exercise, preferably strenuously and several times per week.
I am not going to back that up with sources. It is easily googled and routinely ignored by people wanting fancy, quick fixes with a lot of flash.
Re accidental death:
I paid accident claims for over five years. Very few of the claims I paid were genuinely "Wrong time, wrong place. Shit happens." Not counting people gaming the system, even most legitimate claims had an element of "Why the fuck were you doing that to begin with???" In some cases, this element was glaring enough to make the claim deniable under the list of provisos that boiled down to "If you are doing something egregiously stupid and dangerous, we won't cover your so-called accident when this results in injury or death."
Some basics you probably already know:
Do not drink or do recreational drugs.
If you do choose to drink or drug, arrange ahead of time to do so under safe circumstances.
Follow the safety instructions on medication or dangerous equipment. Don't make an exception "just this one time."
Do not consistently be a horrible, horrible asshole to people. (I paid a claim where that basically got someone shot.)
If you own guns, dangerous equipment, etc, strictly follow safety practices. No exceptions.