The two surviving Japanese schools differ over method, and the difference is instructive.
Rinzai, descending from the Chinese Linji lineage, works with koans: cases drawn from the recorded encounters of earlier masters, presented to the student, who must respond to the teacher in private interview. Many are constructed so that no discursive answer will do, and the function is to bring reasoning to a halt so that something else can operate. Progress is marked by passing a curriculum of cases, and the tradition speaks of a breakthrough, kensho, seeing one's nature.
Soto, established in Japan by Dogen in the thirteenth century, emphasises shikantaza, just sitting, and Dogen's distinctive teaching is that seated meditation is not a technique for producing awakening but the enactment of an awakening already present. Practice and realisation are one thing, not means and end. On this account looking for an experience is itself the obstacle.
Two clarifications matter for anyone reading about Zen from outside. First, sudden awakening is not quick awakening. The insight may be instantaneous; the training around it is lifelong, and both schools maintain monastic discipline, long retreats and years of study. Dogen practised for decades. The idea that Zen is an unstructured spontaneity is a modern Western construction, encouraged by mid-century popularisers and not recognisable in a Japanese monastery.
Second, Zen's rhetorical iconoclasm, burning statues, the injunction to kill the Buddha if you meet him, is doctrinal instruction about attachment to concepts, delivered in a tradition that in practice bows, chants and keeps elaborate ritual. Taking the rhetoric literally and the practice as optional inverts the tradition.