Inspiration

I guess the most important thing about a poem (or really, any creative work) is that it really shouldn't be forced or contrived. Slamming your head into a desk and willing inspiration is not a good way for natural inspiration to arrive unless you want to write a natural poem about slamming your head into a desk. The nice thing is that inspiration usually comes when you start to walk about or even do something as simple as take a walk outside. Experience is the greatest fodder for inspiration: Even if you haven't learned anything new, sometimes seeing something in a new light unlocks new connections in the brain.
In any event, inspiration is also a learning process, as the things you think of as inspiration increase the more inspiration you get. One thought leads to another, sometimes leading to three or four ideas at one time. When inspiration runs low, there may be more ideas left waiting around from previous brainstorming sessions.