The word "spiritual" chafes me. In my lectures at Geneva, I try my best to avoid the word, or if I must use it, add the proviso that it doesn't mean some nebulous, ecstatic experience of unknown quality, origin, or duration. The word is overused to mean anything mystical or mysterious or supernatural. It shouldn't be so. The word "spiritual," in the Christian tradition (however those who aren't Christians want to use the word is fine by me, I'm speaking of how the followers of Christ need to be careful about their language, as I've written before), means "of the Spirit", that is, from the holy Spirit of God.
In other words, to be truly "spiritual" means that we follow the Spirit. The Christian tradition, however, has not necessary agreed with my definition of the word, instead often opting for a more mystical and (frankly) dualistic meaning of ontological/metaphysical oneness with the "divine". So the great masters of spirituality become the Desert Fathers, folks like Julian of Norwich and Meister Eckhart, and modern day teachers such as Richard Foster. Not all go to the lengths of outright Neoplatonism that mystics are famous for, but the language they use often leads down that road. The dualism between body and mind or body and soul that Neoplatonism often produces is firmly rejected (albeit indirectly) in the Bible. Elevating contemplation of God above earthly work is the hallmark of the monastic tradition and has, in my opinion, caused much harm to the work of the Church throughout the centuries. Not that the faith and hard thinking of these folks is without warrant or inauthentic; I consider it on the right road, but going in the wrong direction.
This isn't to say that I don't find much good in these writers either. The extreme devotion to God found in monasticism and contemporary practioners of the spiritual disciplines is something worthy to be emulated, even if the end result needs to be different. If the end result isn't to be some mystical/metaphysical union with God, what should it be?
The ancient debate was always whether man was more god-like or animal-like. Different philosophies held different views and all had vast social consequences. The debate has never, to my understanding, been resolved. The question that I have, however, is why the testimony of Genesis 1 has consistently been ignored: man was not created metaphysically like God, nor was he created as an animal; he was created as a human being--a totally separate category. He is under God metaphysically and ethically and over the animals royally. Authentic spirituality, it would seem, would be to make man not more like God ontologically, as this is impossible, but to make him more truly human, more in the image of God ethically than he was before. Since Jesus is the true human, the point of spirituality is to become more like him (such as is found classically in Romans 8).
Jesus' whole life was guided by the Spirit. He was conceived by the Spirit in his mother's womb (Luke 1:35), baptized and filled by the Spirit at his baptism (John 1:14), cast out demons (an ancient word, I'm finding out, for pagan deities) by the Spirit (Matt. 12), and was raised in a Spirit-animated body (I Cor. 15). An authentic spirituality, one with teeth for the (post)modern world would follow this Spirit-filled man's teaching concerning how we can be truly human, starting (most likely) with the Sermon on the Mount, which is an elaboration and realigning of the ignored and maligned (by the people of God no less!) Torah given through Moses.
The question, though, really isn't "what" of spirituality, since the answer has always been there. The question is "how". Here is where I've found the most help from the "classics" of spiritual devotion. They often developed elaborate and complicated "rules" of spirituality, such as the famous Rule of Saint Benedict. He divided the day up into seven sections, based on Psalm 119:164, "Seven times a day have I praised you," in which the monks would stop their work and join for prayer and the chanting of the Psalter (if only those of us who are Reformed Presbyterians had such a devotion to the Psalms!). The idea of "rule" for life is powerful and seem like a suitable idea to building an authentic spirituality: one that connects the devotee to God, not in transcending humanness, but by using our humanity--which is time-bound--to honor Him. Another reference, found in Deuteronomy 6, seems to lay out a rule for life:
"You shall teach them diligently to your children, and shall talk of them when you sit in your house, when you walk by the way, when you lie down, and when you rise up."
The day, here, is broken up into 5 sections, each with a community involvement (whether familial or in the larger, reconstituted family of the Church) and each involving, significantly enough for us silent moderns, speaking. Silent prayer, while having a Scriptural place, is not the main way used. This does not, however, complete the "how" of spirituality, but it is a step in the right direction, I think.