I can suggest a few steps that you can follow :
1. Quit bad habits like smoking, drinking alcohol, eating junk foods etc.
2. Get proper sleep at night
3. Regular exercise everyday
4. Eat healthy food
5. Regular Medical checkup
6. Keep your mind happy
7. Avoid stress and be relaxed
8. Always smile

There are many other factors too. But I hope, maintaining above points will help you a lot.
Thanks...