Read an assortment of classic and contemporary poetry to get a feel for excellent poetry. Examine Shakespeare's sonnets, Romantic poets such as Lord Byron and William Wordsworth, Victorian poets such as Sir Alfred Lord Tennyson and Elizabeth Barrett Browning, famous modern poets such as T.S. Eliot and Ezra Pound and contemporary poets such as Maya Angelou and Seamus Heaney. Note the different structural styles and diction choices. Consider why people have considered these poets great over the centuries.
Set realistic goals for yourself about what kind of poem you want to write. Decide if you want to create a traditional, structured poem with rhyme and meter, create your own structure or write in free verse, which means you follow no structure at all. Consider the type of diction, or language, you wish to incorporate. Select a style of writing to aim for. Simple writing can be quite powerful.
Choose a topic to write about. Keep it simple and specific. You might be tempted to write a poem that spans history and the universe like John Milton, but sticking to a simple topic you know well is more likely to produce success. A topic could be as simple as a single object, a person, a feeling, an event or an image.
Select a narrative voice. Decide if you want the narrator to speak in first person ("I" and "me") or not refer to herself at all.
Plan out the setting, mood and tone. Jot down words that portray such a mood, such as "ebony" or "depressed," for a dark atmosphere.
Decide where your poem is going to go. That is, ask yourself how your poem will begin and how it will end. Determine where you want to take your reader or what you would like to convey to your reader.
Draft your poem. Without worrying too much about structure, get your ideas down on paper.
Organize the ideas in your poem into different lines, and add punctuation as you see fit. Punctuation should help guide the reader along, telling him where to pause.
Leave your poem alone for a few days, or even a week. Come back to it again, crossing off words and rewriting phrases, always aiming for conciseness and brevity. If you can find a simpler way to express an idea, use it.