I listen mainly for good drum breaks that are isolated (no other instruments playing etc) hopefully a nice instrument melody or stab, something I can loop up and still have a few variations to layer/stretch out into a nice 8-16 bar loop for a verse, then if I'm lucky there will also be a nice build I can use as a pre chorus for a song. Also don't be afraid of sections with drums in them, as long as you chop the sample up at the hits, you can replay the tune to your liking and then layer your own drums on top - once I learnt that I found a lot more of my vinyl samples were usable