An epigraph is a short quotation placed at the start of a poem to help set the tone and focus your efforts. Almost anything can work if you find it inspiring: a quote from another poet, a few sentences from a news article, a memorable phrase spoken by a friend, a saying from Poor Richard's Almanack.
A poem's form is partly visual: its look on the page. George Herbert's "Easter Wings" is an example of striking visual form, as is e. e. cummings' "r-p-o-p-h-e-s-s-a-g-r." But visual form also works in less obvious ways. The lean, spare look of most Emily Dickinson poems complements her terse style, while the long, sweeping lines of Walt Whitman accentuate his bold, expansive message.