Decide what you will write about, and make some notes about that subject. For instance, if you want to write about a person, write words or phrases that remind you of or describe that person.
Choose a fixed form or free verse. For novice poets, free verse might be an easier way to go because you will not have to worry about staying true to the meter, rhyme scheme and length of a fixed form.
Use the images, words and phrases you wrote down in Step 1 to begin assembling your poem. Think about a goal for the poem --- what do you want it to say to the reader? A goal can help you discover a point for the poem itself.
Time yourself when writing a first draft. For example, give yourself 10 minutes to write the first draft of the poem. Oftentimes the first ideas you come up with are the best. Simply write the words and phrases that come into your mind.
Revise your poem. Put the poem away for a couple days and come back to it. Find places where you perhaps used clichés and make those phrases into new ideas. Find phrases where you used abstract words and replace them with concrete ideas. Utilize figurative language like metaphors and imagery. Remember you can always revise the poem again.