I think you’ve just got to find what works for you.
In general, I just use vinyl. Aside from that I’ll play bass on top of things and more recently I’ve been recording myself playing around with synths and what not.
I just do hip hop. I could tell you about how I use vinyl because of how it sounds as opposed to mp3s or whatever but it’s mostly just how I learned. It’s easier to jump around. You can look at a record and know that there’s going to be some kind of break or a quiet part with some open instruments. You can play around with the speed before you even sample anything. I can easily play it against what I’ve got going to see if it might work together. All that.
It does take up a lot of space, it does add up money wise even if you’re not going after rare records, and I think I’m part of the last generation that got a head start with digging by raiding our family’s collections. I used to have the dumb, very late 90s hip hop, sampling rules thing in my head where you have to get it on vinyl or it somehow doesn’t count. Now I’d say take it how you can get it if it works for you. But I still prefer records.
As far as stuff other people have sampled goes, I’d say it’s actually a great place to start actually. Whosampled.com will let you see what records were used in a song and they’ll even timestamp the bits that were used. That can help you get a feel for the kinds of things people you like are sampling and point you towards how they’re using it.
Lastly, I wouldn’t worry too much about whether or not something has been sampled before. Odds are pretty decent that if you hear something on a record someone got there before you and already heard that part. It’s more about what you do with it than anything else anyway. Even if you’re taking a loop, you’re probably going to have different drums, bass, etc.
