My local recordstore, sometimes I go there with a mission "look for this, and then get some other shit." but mostly i just go there and dig for stuff I think looks intresting and fits my prefrences.
I think its easier to find samples on wax since you dont have to know what to search for + sampling youtube usually doesnt have the same quality.
I would suggest asking yourself "what do I like?", - if you dont know what you like its kinda hard to find it. I like certain styles and I go to those sections in the record store. Also looking at the back of the covers hints what the music will be like - If theres 10 artists featured on a track its probably gonna be quite crowded and therefor hard to sample (this logic isnt across the border, its just guidelines)