For me it's a case of looking through the nearest carton of 'the collection' and wondering what will sell without a lot of trouble. Do I feel like packing cartons of books, or just magazines? Am I relaxed enough to check every one of the 800 pages or so in a 1914 'Boy's Own Annual'? Is it worth the time, as in will the final price cover my effort, or will I forget about books and dig out something easier and lighter to pack? You can be sure that books arrive at my door, I don't need to go out looking. Truly! All the locals know I wheel and deal in books and magazines as a combination hobby and bill-payer and often stop me in the street with a "I had this as a child and I'm sure you'll give it a good home". Of course I will, even if it has to go through a chain of friendly until it reaches its 'home'.