These are all great suggestions. My overriding philosophy is look at every part of your boat (mechanical, electrical, standing rigging, running rigging, anchoring) and make sure you have a tool on board to remove/install/tighten/loosen/replace everything. At the same time, make sure you have one or two spares for every nut, bolt, screw, electrical connector, filter, etc. Organize by location/type - a bag/box for engine tools and parts. A bag/box for electrical tools and parts, a bag/box for plumbing tools and parts, a bag/box for extra blocks, extra shackles, extra clevis pins and ring dings (lots of those in assorted sizes), etc. Sail tape and electrical tape to tape over cotter and clevis pins so they don't work themselves out.