i recon do it in 3 stages 1: get two of the same song, play em at the same tempo and get them beat matched so you know what you're listening for. 2. mix two different songs, ones at different tempos (this is where you cover the BPM and use your ears) 3. learn where to beat match (phrasing is the term you're after, heres some info: http://en.wikipedia.org/wiki/Phrasing_%28DJ%29 )