The trick is simple. Use YouTube.
(1) Choose a song that you like or want to dance. Let's say, "Poema".
[1925 original by Canaro]
(disclaimer: I don't own these videos and all rights belong to them)
(2) Go to YouTube and search "Poema tango dance". The search will bring up hundreds of results.
(3) Watch 20 of them from the top. It would take 70 minutes or so (3.5 minutes x 20).
With 20 repetition, you'll get used to the song (not to say bored). You now know how this song goes, where the tone of the song changes ("Poema" is a mix of sweet vocal phrase and energetic instruments, creating interesting mixture of "sweet and sour"), overall structure and refrains of the song, and so on.
(4) Now, you have 20 references to choreograph the song in 20 different ways.
You know how other dancers started the dance, how they danced to the first vocal introduction, to the violin phrase or to the piano arpeggio, and how they ended the dance.
Some of them you may like, some of them you may see as not so effective.
(5) Pick up the moves and musical interpretations you like. Use the reference in your next dance with "Poema". There is no patent in dance moves.
(6) Continue on watching and keep adding (optional).
You are not going to get a Ph.D out of this research. For practicality's sake, input from 20-30 videos are plenty for your output. You might want to consider research input/output ratio.
(7) Pick up another song and do the same.
Each song is different in the mood and contents. Some moves that look nice with "Poema" may not sit well with "Libertango". You figure out what works for the song.
Tango is a traditional art, and the songs have been around for decades. The same songs were danced by many different dancers. You can use this referencing trick.
Salsa songs are used in more metronome-ish ways, and contemporary songs (for WCS for example) may not have so many videos yet. Yet, referencing can work in the same manner.
Creativity is coming from existing body of knowledge (references). Imitation is the first thing you do in dancing. Later you remix them. It becomes your creation.
With this method you are basically "crowd-sourcing" your choreography. Since there are so many references for dancing, for free, why not use them?
