The religion which works is direct experience of God. Any effort which aims at that is true religion.
Religious orientation can be expressed from least valuable to most:
Atheism--no belief in God, no experience possible.
Scientific atheism--belief that God set up the Universe and walked away,no experience possible.
Fundamentalism--belief that a favored few experienced God in the past,no current experience possible.
Guruism--belief that a certain charismatic man experiences God, but I probably can't
Asceticism--belief that I could experience God if I were tough enough on myself.
Shamanism--belief that a particular ritual will lead to experience of God.
True religion--knowledge that everyone can and does experience God directly.
The last orientation is not shared by many of the organized religions. There is great fear that someone, following his own bent, will be led astray. If I experience God directly, then there is no need for any form of mediator. If everyone is his own authority, we might have to actually trust that God's plan is real and unfolding. There is, under this conception, no way to enforce rules on anyone else from religious grounds.
Access to God is not automatic,however. Access requres relaxation of the survival or thinking part of the person. While this can occur with experience, I believe it is better done with a practice. Practices come in lots of forms and have differing degree of effectiveness. The search for a good one is often the main entertainment in the spiritual search.
Thoughts on Life after death here.
Religion is not useful if it does not comfort. The real existence of a loving God who will always help with our hurts and fears, and the existence of a joyful life after our time here is what we all seek in religion.
It is unfortunate that so few religious experiences achieve this aim.