I write chord progression, then jot out what I want in words.
Like:
Intro: Moving synth pad, with intermittent taiko drums. Eventually moving into rhythmic stacatto strings.
Verse: Powerful french horn melody, violins double the melody 2nd time through.
Chorus: Bring in 2nd harmony for chorus melody.
Interlude: Bring down the intensity, to something very calm. Using spacious synth pads, and ethnic flute. Build up toward the end and...
Chorus: Reprise of chorus. Pull out the stops with heavy brass, strings, taiko, etc.
End: Abrupt end, with pause. Then a final "beat" using taikos. Trailer like.