My best results from online dating (and I've had some great results) have come from being very brief in my initial communication, asking a question but not sounding too interested... Give them something to respond to. Not something boring, either. I spammed messages based around "Would you rather fight 100 duck-sized horses, or one giant horse-sized duck?!" at girls for a couple of days once, that did OK.
I've never scored any results from an opening message longer than three or four sentences. I also never tried a copy + paste message, although people do that and apparently do well from it.
I've had situations where I give my number after 8 messages and they call me, situations where they gave me their number after about 20 without me asking, and one situation where I swapped something like a hundred messages with a girl before we got a hotel and had awesome secks - don't EVER think there is one perfect formula, because women are all different and you need to play it by ear. Improvisation is the one great skill, probably in every area of life, for me anyway.