There is no personification (personification is giving inanimate objects human attributes; therefore, if we go by this definition (see www.dictionary.com), the horse would not count since it is not inanimate) or significant alliteration in this poem, although there are a few places where there are 2 repeated consonant sounds. The main element is iambic pentameter, which involves the form of the poem. eNotes states that:
"Iambic" means that each metrical foot contains two syllables, an unstressed one followed by a stressed one. "Tetrameter" means that each line contains four metrical feet. So a poem written in iambic tetrameter would contain a total of eight syllables in each line.
Also, the poem has a specific rhyme scheme, as well. See this link: http://www.enotes.com/stopping-by/style.
**Anthropomorphism is the term for giving human characteristics to animals. Thanks, linda-allen!!!**
There is definitely personification in the second and third stanzas. Personification is attributing human charactersitics to the non-human. Enotes specifically defines it as "a figure of speech in which abstractions, animals, ideas, and inanimate objects are endowed with human form, character, traits, or sensibilities." So when the speaker says that "My little horse must think it queer / To stop without a farmhouse near" and "He gives his harness bells a shake / To ask if there is some mistake," he is giving the horse, a non-human, the ability to think and ask questions much in the same way that a human being would.
There is also a fair amount of alliteration, or repitition of beginning consonant sounds. Some examples are below:
watch his woods (repeated w sounds)
his harness (repeated h sounds)
sound's the sweep (s sounds)
For more information on the style Frost used in this poem, see the link below.
Other links explain personification and alliteration.