What are the Major Steps of the Spiritual Life?

Fr Staniloae gives us a clear view to answer this question  He says there are two phases. The first is the practical phase and the second is the contemplative phase.

The practical phase involves taking actions that help a believer overcome their attachment to passions and progressively learning to practice the virtues leading to love. The purpose of this phase is to become liberated from the passions. The mind must be cleansed and become dispassionate so it can go onto the last phase of contemplation undisturbed by passions. 
He says, 

"Only a clean shinny mirror, unspotted by passionate attachment to things of the world, is capable of receiving divine knowledge."

The contemplative phase is an exclusive focus on God. It is a "reintegration, unity and simplicity." The mind becomes empty, cleansed of passions, quiet with peace and tranquility, now able to receive and accept divine knowledge.

There is a final stage which he calls the theological or mystical contemplation of God.

In the beginning our aim is purification. We must first strive to become able to live the virtues as tough by Jesus Christ. It is the virtues that combat the passions. So it is like a two dimension struggle. Pursue a virtue and eliminate a passion.

When we move towards contemplation we begin to see the reality of the universe. Our object is the "logo" of created things. This is the true meaning of them in eyes of God. One begins to see everything from a spiritual perspective.

Once the inner nature of things is known, then one enters into the understanding of mystical knowledge of God Himself. He says this is "an ecstasy of love, which persists unmoved in a concentration on God."

These steps are similar to the idea of purification, illumination and perfection which was used by Dionysius the Areopagite.

Reference: Orthodox Spirituality, pp 69-73