This set of videos, via DubSpot, takes a look at dubstep composition in Ableton Live.
Starting with a basic beat, Ableton instructor Steve Nalepa uses the Impulse instrument to make a basic beat and then shows some tips on how to make it more interesting.
Check out parts two and three in the series, below, to watch the track take shape.
Dubstep in Ableton Live Part 2
Dubstep in Ableton Live Part 3