Know your audience. If you are publishing poetry for teens, you should familiarize yourself with the poetry that teens are reading -- and writing. Read publications such as Teen Ink, Cringe, or Digital Passions, an online publications. You should read a variety of authors -- male and female -- looking for themes and common imagery. This will help you immensely with your own writing. And there's nothing like hearing poetry spoken aloud, so attending teen poetry slams may be another great asset to you.
Get down to writing. Incorporate into your work some of the themes and imagery found in the poetry for teens that you researched. Fads, topical news, depression, angst and rebelliousness/battles with authority are common, as are universal themes such as love. Free Verse poems may be easier -- and common among poetry for teens -- to write than form poems, but you will find all kinds of poems published for teens.
Rewrite. Rewrite. Rewrite.
The rewriting process is in many ways more important (and certainly more time-consuming) than the writing process. Most finished poems are not first drafts; often they are the 31st drafts. There is no number of revisions for a writer to do before declaring a poem done. But don't be so critical of the work that you never think it good enough. The more you write, the more you will know when the poem is complete.
Find the publications to which you will send your poems. Publications such as Poetry Magazine or the annual Writer's Market, which has listings for lots of poetry outlets, include those that would accept poetry submissions.
Send your poems for publication. Remember to follow the submission guidelines for the publications to the smallest detail. Chances are you will be rejected by several publications, but this is normal. Send poems to as many publications as you can. While it is good to listen to some of the criticism from rejection letters, you are not obliged to make any suggested changes. Just because a poem gets rejected by one publication does not mean it won't be accepted by another.