- Contrasts "Ask not what your country can do for you, but what you can do for your country"
- Three-part lists "Where the strong are just, and the weak secure and the peace preserved"
- Contrasts combined with lists (by contrasting a third item with the first two): "Not because the communists are doing it, not because we seek their votes, but because it is right"
- Alliteration "Let us go forth to lead the land we love"
- Bold imagery "The torch has been passed to a new generation of Americans"
- Audience analysis
There's lots more good comment on this subject in a BBC article and in Dr Max Atkinson's blog.