The first step is to know what you are talking about. Not only in this question, but I mean that in every moment of life, on any subject.
If you are discussing God, heaven and hell literally, but there is no way we can understand these things as a normal human no matter what you would like to imagine, reality is that this is probably not possible, the question becomes a distraction and diversion from the present moment.
Thus the question is an abstract idea like a Picasso painting, a very distorted individual view. I suggest you forget these concepts and just focus on being happy each moment, meaning doing what is in front of you, being present, not living in past or fear of future.
Be active and productive every day. This will calm your mind and a calm mind is one that is in a ‘heavenly’ state. If you want to search for anything abstract, then search for yourself. Observe your feelings, for example, the physical sensations of being happy and elated or depressed.
Feel the movement in your body, your chest, how there is a physical change in your body with your moods and emotions. Observe your mind, how it moves with identification of events. Practice self-observation of your responses to things people say, to events you hear about and happen each day.
Notice how when you get some good news you are elated, and can feel a rising sensation in your chest, but when bad news comes, how your shoulders slump and a heaviness brings down your chest. In observing all these physical sensations that happen when nothing physically has touched your body, you must come to a realization that there is more to a human than just a body and thoughts.
There is something very real, physical, that is our ‘spirit’. Think of expressions such as; ‘lift your spirits’, or being depressed, and observe your physical changes that make them not just expressions, but statements of physical reality.
In this observation, you should start to change your view of life by the proof that there is something non-physical that changes with our moods and that we can control by consciously lifting your spirit when it becomes depressed.
I mean that as a conscious, physical action, although done with the mind. It is an actual moving of the energetic ‘ball’ that moves lower in your torso or higher, and as it moves, so does your mood. You can move this ‘ball’ and change your mood, either up or down, no matter where it is moved by events.
Our mood is very much alterable with our own mind, if you really want to feel better. I am no enlightened master, I am just a guy who observes and has discovered things, and through that, has an ability to see things that other people miss. This is how you can get the same ability. Forget heaven and hell and God, and just observe yourself.
The Sufi say; “He who knows his Nafs (self) knows God.” Shakespeare said; “To thy own self be true.” not someone else. The New Testament says; “Know thyself.” There are many more. The answer to knowing God, heaven and hell, and even happiness, is out there, but so simple no one wants to listen, also because no one wants to really know themselves.
There is no doubt that just about everyone does not want to really know themselves, because of fear of finding out what you really are like. This is what keeps us from seeing the simple truth about our world.
Put the effort in to studying your mind and emotions and also your body on a physical and energetic level with the same curiosity that DaVinci had when he wanted to know how the body worked, and dissected as many corpses as he could find.
Observe yourself and learn what a human being really is, and maybe then with that knowledge mastered, maybe you will be lucky enough to understand things beyond.