Musically
there are a couple of things that immediately spring to mind
in regards to writing the Bridge. Fool around for a while
with the relative minor (or major, if you wrote the song on
a minor key.) This is usually good for a couple of ideas.
Second; mess with the rhythm in this section. Sometimes a
triplet feel is all it takes (listen to the Beatles song We
can work it out for an example of this.) Third: sometimes
the Bridge is an instrumental section. If this is the route
that you decide to choose, remember that wherever the musical
journey that you take the listener on here goes, the Bridge
must resolve to the Chorus.