The two articles that David Jalajel mentions in his comment below are published on The Ghazal Page: "A Short History of the Ghazal," and "Rules for Writing Arabic Ghazals in English."
Be sure to read Dreamgrass's comment on this post. He wrote the wikiHow entry on ghazals; his comment explains the thinking behind his entry. Very much worthwhile.
This post responds to a couple of recent comments. In the first, Niranjan Sarkar clarifies a misconception in my post "Performing Ghazals." Contrary to the impression given by some Web sites, the ghazal is originally a form of poetry, not of lyric written for music. I appreciate this clarification, especially acknowledging that I should have checked out my assumption in writing the post. Niranjan, by the way, contributed a ghazal to the moon radif challenge.
I suspect there's more to be said about the relationship between ghazal in its origins and music. If anyone wants to pursue that question and send the results to me, I'd be interested. They could become an essay on The Ghazal Page or a comment here.
The other comment asks simply, are the instructions for writing a ghazal on wikiHow the "right way" to write a ghazal. The instructions as written would yield a ghazal in the strict Persian form; there are other ghazal forms, notably the Arabic ghazal, as explained by David Jalajel. The Ghazal Page has a wide variety of approaches to the form of the ghazal in English. (Some of these may go beyond the bounds of the ghazal, but they are still interesting explorations of the possibilities.
An early ghazal writer, Francis Brabazon, wrote many ghazals using only qafiya (the monorhyme), as well as some with radif. Like some of those of other poets, some of Brabazon's ghazals are written in rhyming couplets. Other poets do not use qafiya or radif and still produce impressive ghazals.
The article on wikiHow mentions having the same number of syllables in each line. Counting syllables hasn't been used widely in English verse. Counting stresses would work equally well. Effective metrics in English does not require absolute uniformity from line to line; in fact, absolute uniformity can result in great tedium. Even a purist of the Persian ghazal, Agha Shahid Ali, does not discuss meter in his (excellent) description of the form. (He does mention each line being "the same length," but this is the least helpful advice in his article.
Why have I posted my response to wikiHow here instead of editing the article or commenting on it? Mostly a matter of time; it's more convenient for me to put these ideas here. If I have time this weekend, I may add something to wikiHow, but I really don't want to rewrite the article that is there.
Please don't think of writing poetry as a matter of knowing the "rules" and applying them exactly.
Is writing performing? I'll perhaps pursue this point later. Right now, my answer is Yes, but the audience is not immediate and is diverse. The "performance" is in sharing the poem through whatever means.