Well even the Zennist can be read with profitability once in a while. Today, the Zennist points to a paper on the 'net by Stuart Lachs, who unlike the Zennist, or perhaps the author you're reading at the moment, is a pretty reliable source for what it is when it comes to the facticity of Zen, though my intent is to be at least as skillful at disseminating of the true core of Zen as Lachs. I quote:
The Chinese term Hua-t’ou can be translated as “critical phrase.” Literally it means the “head of speech” or the “point beyond which speech exhausts itself.” In Korean, hua-t’ou are known as hwadu and in Japanese as wato. In this paper I will use the Chinese term hua-t’ou exclusively. A hua-t’ou is a short phrase (sometimes a part of a koan) that can be taken as a subject of meditation and introspection to focus the mind in a particular way, which is conducive to enlightenment...
A hua-t’ou however is a stand alone, always short phrase or a part of a koan that can be taken as a subject of meditation and introspection. Though teachers may give talks about working on a hua-t’ou, there are no standardized collections of huat’ou with poetic, often complex commentary as there are with koans that require explication and some knowledge of ancient Chinese metaphor.
Though not widely known in western Zen circles, hua-t’ou meditation is popular in Korean and Chinese Zen. Since the famous Korean monk Chinul (1158-1210) discovered hua-t’ou meditation late in his life, it has been the favored form of practice for Korean Zen monks to the present day. In China the practice began before the 11th century. Hsu-Yun (1840-1959), the most famous Zen monk in the 19th and 20th centuries, practiced and taught hua-t’ou meditation as his favorite form of meditation
The hua-t’ou, though popularized a long time ago, is a good method for people today: it does not require a group or regular meetings with a teacher and besides being practiced in formal seated meditation, it can or really should be practiced throughout the day, even while at work. Hence, it allows for a full time Zen practice while living and working in the world.
Lacks goes on to note the difference between koan (公案) practice, which leads to focus on the 話頭, and shikantaza (只管打坐) practice.
I'm not really certain that 話頭 practice is largely unknown in Western Zen circles - there are a bevy of Rinzai Zen temples here in the West nowadays, as well as Korean Zen temples (not to mention descendents of Hsu Yun and others.) Too, anyone who reads D. T. Suzuki's works on Zen will come across the 話頭 sooner or later.
But I can't but agree with Lachs' later point: the 話頭 - a way of orienting the mind, putting it in a place where critical thought is held in abeyance, is ideally suited for being carried throughout the day. I think it's somewhat of a disservice that is done in focusing on the "sudden enlightenment" aspects of Rinzai Zen. If the thought of "sudden enlightenment" arises in your head, you've lost the 話頭. So yeah, I think the Soto folks sometimes mischaracterize Rinzai practice because they really don't understand it.
And sometimes, descendants of teachers trained in Rinzai Zen make this mistake: it is a fact that some teachers in the White Plum lineage have tried to dissuade students from practicing mu (無 ) throughout the day, but yeah, Lachs is right: doing this in the midst of activity is what teachers from Ta Hui down to Hakuin have recommended.
Over on Barbara's site today, there's an exposition of the religious aspects of Buddhist practice, triggered from a discussion with Petteri and myself. Me, I've been very lucky to come across the 話頭, and a teacher who "teaches" it, to help me get from point A to point B, no matter how close A is to B. There are other ways, to be sure, but this way, done with attention, is well suited for my place in life. And yes, it even is done as a way of quieting the critical mind during the rituals of Zen itself.