The only ways you could actually die is decapitation, being incinerated (like Nepalm, Greek Fire, a nuclear bomb going off), sent into the sun, dropped into a volcano, or crushed (since that also destroys your head). Other than that, you are immortal and unable to die.
The cost of that power is you need to drain the life (or life force) of other humans. That involves a simple handshake or touch. You could drain 10 years or all their life. For adult humans it would rapidly age them, so if you drain someone who is 30 of 50 years, they will experience immediate age progression with white hair, wrinkles, and all the side effects of aging while you will restore your youth, heal any wounds, regenerate lost teeth and repair any eyesight problems, and if you already drained another, you would just bank those years.
Your eternal youth requires you only drain enough from a person to maintain your youth. It will automatically heal any age related issues you experience. Your regeneration and healing require you have 1,000 years minimum of "banked" life force. While your Immorality requires a minimum of 10,000 years. Anytime you use your healing, regeneration, or immorality you use your "banked" life force.