[Q]What to look for in a quality bow

I need to know what to look for. I'm buying a flatbow, and I don't know what a good flatbow entails. I basically know nothing, so please tell me as if you were talking to a five year old.

What should the string be? Should it be thick? Thin? How long should the draw length be? How do I determine this? The material of the bow? I would love some guidance if anyone would be willing to give it.