Don't be impressed by cellophane-wrapped pallets. If you are buying handmade tiles, you don't want machine-made ones mixed in to make up the load. If you are buying long lengths of timber, watch out for short lengths hidden in the middle of the bundle. Remember - examine, count and measure. Talking of examining things brings me on to sanitary fittings.
Toilets are probably the most unpleasant things to buy straight from site.
I remember one bathroom specialist who had no hesitation in donning a pair of rubber gloves and getting down to examine a Victorian loo. He came up elated, declaring that after a good clean 'you could eat your dinner off it' - an invitation I think I'd rather decline. Mind you, if a pan has no damage, once cleaned it will be as good as new. The best advice I can give you is to save your cash. It is important to recycle materials, but buy from a specialist dealer flirther down the line.