Brainstorm a list of words that you associate with snow, such as icy, white, fluffy and soft. Write the words as they come to you; try not to think too hard about the word association.
Write a list of humanistic features, characteristics and attributes you associate with snow. For example, "the snow whispered on the wind as it floated to earth" is an example of personification because whispering is something a person does, not something snow does.
Construct your poem using a theme to help personify the snow. Think about snow like a living organism to craft your poem and choose your words. Saying that "Old Man Winter's breath blew torrents of snow in the air" is personifying the snow; saying that the snow was "fuzzy like a blanket" is not personification.
Set up your poem according to your own personal preference and voice. A poem does not have to rhyme; it can be blank verse or a prose poem, which do not require stanzas. If you so desire, you can write the poem as a sonnet; a sonnet is composed of 14 lines. In the first twelve lines, every other line rhymes; the last two lines are a rhyming couplet. Write your poem in whichever form pleases you most, so long as it employs personification.