It's typical for a song to build to the chorus, starting with a verse and arriving at the chorus via a third melody known as the bridge. "California Girls" by The Beach Boys is a prominent example of this structure. The chorus traditionally is or includes the hook of the song -- its most memorable and hummable bit. Starting with the chorus brings the hook forward in the song and gratifies the listener instantly. "She Loves You" by The Beatles is a prominent example of this technique paying off.
Changing to a different key can add emphasis to a melodic idea and, if the new key is a higher one, give a sense to lift to the song. There are various types of key change. In some cases, the entire body of music is modulated to a higher key. The final chorus in "Man In The Mirror" does this. Sometimes just the backing changes key, while the top-line melody remains the same. The final chorus in "There She Goes" by The Las shifts from a D major to D minor. The final chorus in "To Be With You" shifts up from E major to G major, a change of one and a half steps.
Extending the last chorus adds emphasis and increases the chances of the hook staying with the listener. If the chorus is normally four bars, extend the last chorus to eight bars. As well as repeating the hook twice as many times, the repeated chorus serves as an indication to the listener that the song is coming to a close.
Instrumental breaks, or solos, are an effective way of breaking up a song, giving band members their moment to shine and also of adding a new flavor to a song. A good solo is one that explores the main melody of a song, but adds something to it. For example, in the guitar solo on "Smells Like Teen Spirit" Kurt Cobain plays the chorus vocal melody on the guitar. He uses a distorted guitar sound to add a new dimension to the overall mood of the song. Some solos have no relevance to the rest of the song. While this is an arrangement technique in its own right, it is a risk to take the song off on another tangent.