I usually look for songs with no lyrics (so instrumental) that has a good beat to it, preferably kind of techno. If the song does have lyrics, it needs to make my tricks flow smoothly. My favorite yoyo music:
w/o Lyrics:
Razor Sharp, by Pegboard Nerds and Tristam
Flight, by Tristam and Braken
w/ Lyrics
Paparazzi, by Lady Gaga
Pride (In The Name of Love), by U2vsTiesto