You read other poetry, you compare. You take a creative writing class, you ask your friends to read it and get criticisms. You go to poetry slams/readings and listen for a response. If you get a blank look, try a new approach, if you keep getting them, then perhaps you should write in other forms, if you get a good reply... then take that encouragement. If you wanna learn how to start, you just do. Get a journal, a pen and write. Use a thesoris and edit some of what you've written. Play, play, play with different styles. Find other peoples work you like, and try adapting some of thier style. Eventually, you will find your own, you will find your own style and you won't wonder anymore if you can write poetry, you just do.That's whats happened to me, and continues to everyday for the last 11 years. Good luck!