A reader beginning a poem is like someone stepping into a rowboat with a stranger at the oars; the first few draws on the long oars through the deep water tell a lot — is one safe, or is one apt to be soon drowned?
– Mary Oliver

A simile to help one recognize a “good” poem.

A Poetry Handbook might be the modern Rhymester

Oliver, Mary. A Poetry Handbook. Taiwan, Harcourt Brace & Company, 1994. pp56-57