I like to sample from film scores the most, there's so much variety from film score composers that it never gets boring.. But I like to sample all types of stuff.. Foreign stuff is great to sample too, but I also sample a lot of rock, some funk, jazz, etc.. I rarely sample soul though, because in my opinion soul is getting played out in hip hop samples, you can thank 9th Wonder and Kanye West for that, but occasionally if I find a real gem that I've never heard flipped I'll give it a shot..

If you're just starting out with sampling, just sample whatever you think would be dope and keep building. It will take a lot of experimenting to find your groove.