Practice is what one does in response to one's understanding of life, and being. Practice consequently changes as one's understanding changes. Life itself is a process of change.
Practice is simply living one's life fully and completely, based on sound principles that respond to life's conditions; as do Buddha's Principles. Principles respond to real needs of the present moment and present situation, including one's thoughts and feelings as well as one's relationships.
It takes a book, if not one's life, to understand Practice. Stephan Batchelor, in his book "Buddhism without Beliefs" characterizes Buddhist Practice as what Buddhists do with respect to Buddhist principles. Thich Naht Hahn's small book "Be Still and Know" includes "Peace is all around us, in the world and in nature, in our bodies and our spirits. Once we learn to touch this peace, we will be healed and transformed. It is not a matter of faith; it is a matter of practice." Peace is an ideal among many, e.g., love, compassion, kindness, truth, and equanimity, and Thich Naht Hahn's statement applies equally to each Ideal. From Dogen's book "Beyond Thinking", edited by Kazuaki Tanahashi, "spiritual practice is not some kind of striving to produce enlightenment, but an expression of the enlightenment already inherent in all things."
Kosho Uchiyama's "Opening the Hand of Thought" describes key practices while omitting details of Zen practice such as chants, ceremonies, and bowing. In his concluding chapter, Uchiyama's final talk before retiring after ten years as abbot of a Japanese temple and over thirty as a monk, Uchiyama strongly advocates and discusses seven points of practice:
Uchiyama's teacher, Kodo Sawaki Roshi, was among Kobun Otogawa's teachers. Perhaps a key point, in Sawaki's words, is that "Zazen is the self doing itself by itself ... the (universal) self selfing the self". Self is ubiquitous in Uchiyama's expression of Zazen, that returns Zen to its roots as our flesh and bones practice, rather than our intellectual understanding. Self becomes increasingly evident as one's practice "opens the hand of thought". Uchiyama's practice, like Kobun's practice, leads one toward a magnanimous and compassionate heart, and an open, reflective and responsive mind.The Noble Truths, Eight-fold Path, and Precepts are listed in Buddhism in a Nutshell.
Kosho Uchiyama, as briefly described in Wikipedia.
Kobun's Teachings on Jikoji's web site.
Kobun Chino Otogawa Roshi describes Kobun.
Kobun's Discussions is a series of his earliest discussions, from 1973.
Mind and Meditation