Get a tracked out version of the sample?
No, really, you're going to have to get really creative for that kind of stuff. You can either:
a)try and find the parts you want by themselves on the song you're sampling.
b)get some live musicians to do it for you.
I've also tried eq-ing the sample to accentuate the sounds I want while dulling the others and doing some fancy filtering to cut off some unwanted frequencies. However, this will result in a totally different sound that you didn't have in mind for the beat. Who knows? It might sound good.
It also helps to make the other instruments work with the beat. I've used horn hits off records, and the guitar lick in the background matches the beat perfectly and sounds great!
You're best bet is to do everything and anything you can to get the sound you want. Don't think of making beats as a checklist to fill out, but an experiment you get results from.