I’ve spoken here occasionally about God Realization. I wanted to add some further notes on the subject.
Firstly, it’s good to know that evolution happens both ways – from the outside in and from the inside out. We have a spiritual practice to awaken and Self has a process to wake through us. Put in this context, we go to meet God and God comes out to meet us.
Also, before God Realization, we have to know who we are. Self Realization has to come first. Self awakens to the Self through you. Then God Realization can really begin.
From the inside out, the fullness of Self within begins to overflow, it moves forward and absorbs fine feeling (hence the heart expansion). Then it absorbs mind and thinking, then out into all of our experiences. Maharishi Mahesh Yogi describes the “fullness of Being overflows” into the mind and thinking, then out into the senses. Adyashanti talks of this as absorbing head, heart, and gut.
From the outside in, we experience growing perception of subtler values (energy and light), then the mechanics of creation. At some point, we come to primary principles of nature & the 5 forms of God*. Finally, we come to the finest of the relative. Here we find the interplay of the 3 gunas, the intellect, and, just beyond the intellect, the field of eternal bliss. We have come to the edge of the absolute, what physics calls the event horizon.
This is where God Realization takes place – where the absolute and creation meet. This is where we meet God in earnest, whatever our prior experiences may have been. It doesn’t matter what we believe or don’t believe or what concept we have about any of this. Now it is our direct experience. We can say God becomes self-evident then directly experienced.
A deeply intimate relationship develops, one much closer than anything we’ve ever experienced. God and Self are now as close as the absolute and relative.
Here’s a few quotes from Maharishi from his translation and commentary on the Bhagavad Gita (p 443-7)
“Where perception of everything whatever is perception of Being made manifest”
God Realized, one “moves on earth and lives in the land of God.”
“They share their life with God”
We see God “abiding in all beings”
(his commentary is well worth the read)
Unity
Gradually we surrender more and more to God until we’re so close, there is a unification. Even if we’ve already had the Unity shift (ending the separation of inside and outside), it is not until this stage that the unity can reach any kind of completeness. Everything must join together, including with God, for Totality to be realized.
As we join God, the absolute and relative aspects of life are also joined. Together we contain all.
Its notable here that there is a choice in unification.**
1) Personal
We may take a Personal route and retain a small gap, a Leisha Avidya or remains of ignorance. A small separation to keep the flow of love and devotion to God. We continue to play with God.
or
2) Impersonal
We may choose the Impersonal route, the route of complete Oneness with God. We surrender even our relationship with God. God becomes a part of us and we a part of God.
This choice is between you and God. There is no point in considering advantages of one or another. You’ll know what is best when the choice arrives.
This final step is more than God Realization. Maharishi once called it Unity in God Consciousness. It is the ground of what he later came to call Brahman Consciousness. Back on the Mahavakya page, this article is about Tat Tvam Asi, Thou art That.
This all may seem far out or far off, but it’s really closer to you than the end of your nose. 
Davidya
* The 6 forms of God per Shankara are Nirakar or formless and Pancha Devata or 5 primary forms. How each person experiences them is somewhat unique and dependent on both the person and deva.
**[Update: Note that Personal and Impersonal also apply to our approach to the personal qualities of reality. Broadly, Personal is the more feeling devotional path, Impersonal the intellectual path. Devas vs laws of nature, for example. In other words, both our approach to reality and our choice of relationship with God can fit in one or other camps. As well, an Impersonal approach does not necessarily mean an Impersonal choice. One may approach intellectually, then melt in the light of God. Or one may approach devotionally and desire a complete merger.]
[UPDATE: When i wrote this article, I was using "God Realization" the way Maharishi was using it - when we have the ongoing experience of the living reality of God. (as in the quotes) More recently, I've begun using "Realization" in the same way as it's used for other stages - when we become. In that case, "God Realization" is the climax when we make the choice described above - to unify fully or retain a small separation.]