My approach so far has been to choreograph the songs which seem to beckon dances more readily. (Translated: I'm doing the easy ones first.)
First dance: Surrender.
The very first time I heard ELO's Surrender the entire premise, look, and feel of the dance popped to my mind, ready-made. The mood and story of the dance remained virtually unchanged from the moment I first heard the song. All that remained was to zoom in on the actual choreography that would convey the story -- and even then I had some of the pieces already.
It's a dance for ten (five couples), but the focus is on one particular couple and the other four mostly make up the setting. It borrows the general premise/theme from story-songs I know and love (Crumbächer's Jamie, Steve Taylor's Jenny, Veil Of Ashes' Angel Falls) -- a naive young girl gets flattered (or perhaps pressured?) into a sketchy romance. The featured couple meet at a dance, they 'fall in love' and start dancing together, but throughout the piece the guy starts getting more and more possessive and the subtext becomes darker and darker, meanwhile the girl keeps ignoring the alarm bells that surely must be ringing in her head. The whole piece builds to the end pose: they're suddenly alone, and she's in his clutches -- literally. It could be a jab at rape culture, it could be a jab at hookup culture -- I'm not exactly sure where I'm going with this one yet, but it'll be dark, in the vein of Daniel Amos' Doppelgänger (think Real Girls).
Second dance: Love Divine.
The is an adorable Phil Keaggy song with heavy Beatles influence. The first time I heard this, I knew it was a duet and I knew what the costumes would look like. Plus the dance's ending sequence pretty much came ready-made with the song (and it took a lot of self-discipline to not use that sequence for the whole song because it worked so well).
This song is a night-and-day difference from Surrender, thematically. Love Divine is a song of joy and love from Keaggy to God, singing about how this love saved him and thrills him. It's infectiously happy. It was a bit strange doing a dance ultimately about the widespread corruption of the concept of love and then doing this dance about the perfect, unadulterated (though certainly misunderstood), and free love of Jesus -- the way love was originally intended to be. I went from choreographing some of the darkest depths to the lightest and sweetest in two days.
What's next: I'm thinking David Meece's Rattle Me, Shake Me.