Have you ever felt that there are so many things on your mind and you have no way to express them? Perhaps you're in a really dark mood and don't want to talk about whatever it is that's on your mind. Whatever the case, poetry can be a wonderful outlet for the inexpressible things hidden away in your subconscious.
Inspiration for poetry may come from your feelings and circumstances, particularly if both are negative. Write down a list of words, phrases and brief sentences describing how you feel about yourself, or something and someone else. Let it rip; don't conceal anything.
Decide on a theme based on your feelings. For example, are you going to write about defeat? Maybe it's not about defeat at all. An array of mixed emotions could see you writing a poem based on moving past defeat and setting down your strategies to achieve victory.
Ensure that the last word of the first line of your poem rhymes with the final word of the third line of your poem. Likewise, the second line must rhyme with the fourth. Alternatively the second line may rhyme with the first, but I personally think some of the best poetry I've read follows the first rule.
Probably the most difficult thing to do with poetry is getting everything to rhyme. The use of a rhyme dictionary can make all the difference.