To write a poem there really isn't any rules, you write what you feel. Commonly, you would make it rhyme but certain rhymes are pretty simple and not very good and they are 'amature' in context.
Since you can't really go wrong with a poem all you need to know is that when you hand something in to a teacher you just got to do these things:
-Have the poem make sense
-Don't swear in it (leave that to personal poems)
-Add poetic devices (teacher's love that)
The END...yes, it's that easy...
