The first time I recognised a sample in music was Spin Doctor's Two Princes, which appeared in Sad but True, by Orbital. I excitedly told my Dad about this, and he told me that sampling was nothing more than theft and was not a legitimate approach to making music.
Years later, he heard some DJ Shadow and was visibly irritated to have to admit that this album made entirely from samples was actually a masterpiece.
Sampling probably hit its peak in the late 80s and early 90s, with Paul's Boutique and 3 Feet High and Rising being musical collage. The clearance of samples (not something that was that stringent back then) is why there is no De La Soul on streaming services before a certain point, though that is set to change very soon.
Famously, to sample Lou Reed on their most well known track, Can I Kick It?, A Tribe Called Quest had to surrender 100% of the royalties and publishing.
I'm no crate digger, but I maintain a playlist of originals and samples that I update as I notice them through regular listening.