Here's an exercise. Take a book of poems and write up what its rules might be.
For example, I'm reading a Latin American poet (excellent by the way) and I notice in her poems the following rules apply:
Everything takes place in a dreamscape. There is no social reality, no other people. (There is a you and an I, but they seem to be the same person. There is one other figure that might be referred to vaguely.) There are no references to daily life and its routines. All poems are in prose and less than a page long. No proper names. There can be no references to modern technology (trains, planes, telephones, cars). No humor is allowed, no variations from a single tonal center, mostly negative and despairing. There are body parts and nature but no bodily functions to speak of, no eating, drinking, smoking.
It's all just the poet's self and existential threats to it. There's nothing wrong with this claustrophobic mode of writing poetry. For me it's great. I wouldn't assume though that everyone will like it and wouldn't really complain about someone who didn't like this kind of thing. It even took me a while to get in the mood for it today.