Hi Andy,
 
More important than where you stow things is recording where you stowed them.  We created an Excel spreadsheet with what we thought was sufficient detail but later found that you can't have too much detail (i.e. now where was it I put that can of contact cement?).
 
Let common sense be your guide.  Place maintenance parts and materials (belts, oil filters, impellers, lubricants, etc.) where they are readily accessible while repair and replacement parts (pumps, RO membranes, charcoal filters, spare propeller, etc.) can be buried in the cockpit lazarette, the space aft of the galley trash bin, or the port space under and aft of  the master berth.  I keep my tools readily available in one of the saloon lazarettes and my wife keeps most of the non-perishable food in another (we have a freezer in the third).  She finds it particularly helpful to 'layer' the foodstuffs with loose cans and bottles on the bottom covered with rubbermaid-type plastic bins holding pasta, flour, rice, etc. 
 
Size, shape, and weight will also help define stowage.  Our sewing machine is a big, rectangular, and heavy piece that would only be happy in the bow portion of the v berth.  Finally, trim of the boat should not be ignored, so distribute the heaviest items along the centerline or evenly about the boat.
 
Hope this helps.
 
Dennis Johns
s/v Libertad, Maramu #121
Bundaberg, Australia