^Take a cutting like you normally would, from a vegging plant, make sure that it has either a grow tip, or a small bud at the tip, and it'll sprout roots, just like any other. The trick, is to not wait too long into flowering. If you wait too late(past the halfway point), the cuttings will become 'woody' and hollow inside, and that's when they become very difficut to propogate. In the first 3-4 weeks, it's quite easy.