Do not write doggerel. To write doggerel, all you have to do is find some words that rhyme in a thesaurus and stick them at the end of a few phrases of roughly equal length. You will find that such doggerel is easy to write. Unfortunately, the results will not be real art.
To write rhymed poems of artistic value, you must first become very proficient in English. You must study grammar and improve your vocabulary so that when you write a poem, the right words and the right usage will come naturally to you.
At the same time, you must acquire a feeling of what type of poetry is truly artistic. Read such authors as Milton, Coleridge, and Gray. Don’t neglect Shakespeare’s plays. You won’t find much rhyme in them, but you will find art. Also, read various works on art criticism like “Ars Poetica” by Horace. If you can’t read the Latin, it is readily available in translation. Study the various meters that have been used in English poetry. If you think that a dactyl is something from Jurassic Park, you are not ready to write.
When your preliminary preparation has been completed, choose a subject. Horace suggests that you start with a theme that has already been treated by other authors, but it is better to write on a subject in which you are interested. At the same time, choose the scope of your work. Will it be a lengthy epic, a short lyric poem, a ballade, or a longer narrative poem? Will you write a sonnet or content yourself with a simpler rhyme scheme? In your first attempts it is better to choose modest projects that are easy to fulfill. A young eagle does not soar to the summit of Mt. Everest on its maiden flight.
Remember that education is a life-long process. Continue studying astronomy, history and geography and you will gradually have a wider selection of material from which to choose the themes of your poetry.
An outline will be helpful. If a short poem is under consideration, at least jot down a summary of what you want to say. A pilot cannot complete a mission unless he knows where he is going.
The final step is writing the poem. Use your sense of rhythm to produce a metrically satisfying work. Use your command of the English language for a satisfying choice of words, especially for the rhymes. Give considerable thought to how you want to introduce your theme, develop it, and write a climactic conclusion.
You may introduce your theme directly, as in “The Rhyme of the Ancient Mariner,” which Coleridge begins with the words: “There was an ancient mariner, and he stoppeth one of three.” Or you may leisurely describe the setting before you arrive at the chief subject, as in “The Raven” by Edgar Allen Poe. If you use the latter approach, make sure that your preliminary remarks lead directly to your theme.
In the development, take care that the unity of the work is preserved. Everything you say should relate to the theme, and there should be a logical progression of thought that builds up to a climax.
When the climax arrives, use all your powers to make it convincing. Do not resort to bombast, but express yourself with simple moving pathos, in a style that accords with the theme and general tenor of the poem as a whole.