around here there is only one really good store that i frequently go to. got everything from new to old there. plus the prices are solid, from the dollar bin records (my favourites) to brand new vinyls and everything in between.
usually i break it down into sections too. i need at least an hour or more for diggin or else i dont feel like i completed anything. but i usually hit every section if possible, or at least parts of each section.
Jazz, Soul and Hip Hop records are what i look for mostly, but then the obscure shit like orceshtral music, just random joints i know will have some gems on there. one thing that helps is vinyl artwork, that shit is bomb and if its got dope artwork imm buying it cause its gonna have some gems on it
that a bit of my process