I believe that caloric restriction is the single most important thing one can do to lengthen life, provided the food is sufficient in nutrients. I have no proof of this. I do know that ever since I've dropped my calories from 2700 to 1600 and maintained for about a year, I've felt better in all catagories.
The next thing that has been said to increase life span is lowered body temperature. Many scientists say that there is a pattern indicating that species with the highest resting body temperature, and the lowest body temperature among that species lives the longest. What you can do about this is limited. I would think that a lowered body temperature would be a symptom of good health and not something one should go about directly changing with medication.
As for taking anti-oxidants (and suppliments), I have yet to see any studies that indicate taking anything above the RDI will help to extend life, lest you had some kind of sickness that would prevent utilization of these nutrients, even then mega-dosing might not help and could have adverse effects- It doesn't seem to help much with cancer patients as far as studies show. Actually the only thing going for cancer seems to be Chemo and faith, at least in my opinion.
And of course 'balance.' Balance in everything- money, food, sex, partying, excercise, mood, bodyweight etc. As for the defintion of balance, your on you own for that.