I was in junior high (7th grade?) and saw somewhere some Cummings poem(s), and thought, That's how words should work: undo them, redo and move them; tamper at the level of the letter. I had jotted his "loneliness/a leaf falls" poem down in a notebook and thought for years I had written it myself. Oops.
A few years later, Peter Gabriel's "So" came out; it has a song about Anne Sexton on it ("Mercy Street"), and that led me to her. I otherwise didn't read much poetry, just sort of wrote compulsively on Post-Its or whatever little pieces of paper were around, having no idea what I was doing, or that what I was making might have been poems. I showed some to an older and more worldly friend, who was impressed enough to write a poem to/for me. There was something crucial to me about that exchange, that support; it revealed to me one of the functions of poetry, for which I'm still grateful.