Pre-launch: Check all your through-hulls and seacocks for signs of corrosion or other failure. Check all below-waterline hose connections and replace any cracked or broken fittings or corroded hose clamps. (And don't limit this exercise to your sanitation system!) Do the same for all your rail stanchions and deck mounted hardware, and rebed as necessary. Bedding compound is cheaper than replacing a water-stained headliner--and a LOT cheaper than replacing rotted fiberglass and stringers. Faulty or neglected electrical wiring is the #1 cause of boat fires. Check all your wiring and electrical connections...and your fuel lines and connections. Charge your batteries and make sure EVERYthing works...replace fuses as necessary...replace any frayed or corroded wiring or switches...any hoses that show signs of chafe. If you have access to water, now's a great time to really CLEAN your bilge, sumps and chain locker--while the boat's out of the water and can really dry out. You won't smell them now, but there are a lot of odor-causing “critters” growing in all those places, just waiting to multiply and STINK when the weather get hot. Pre or post launch: If you haven't rebuilt your toilet in a few years (or ever, if it's more than 3 years old), now's the time to do it--while it's clean and dry. Preventive maintenance--new seals, gaskets, valves, etc--reduce the odds of having to make repairs by 99%. Whether you rebuild or not, if you didn’t do it in the fall, lubricate your manual toilet: open the pump and give it a liberal slathering with SuperLube—the same thick teflon grease that was in it when it left the factory. Not only will it keep your toilet pumping smoothly for a full season, but it will protect the seals and pump housing from grit and dirt. Replace every impeller—in the electric toilet, the macerator, the engine intake--on the boat that has not been replaced in at least two years, even if they look ok. While outright damage can be obvious, ordinary wear is impossible to see. Check all vent lines--on fuel, water and holding tanks--for obstructions and clean them out if necessary. Pressure test your holding tank for leaks. Check hoses for odor permeation and replace if necessary--it's a much more pleasant job in cool weather and when the system is clean and dry than in hot weather when they're full of sewage. Replace check valves in vented loops. Don't forget the fresh water system. Follow the instructions in the article "Fresh Water Maintenance" for recommissioning your freshwater tank and plumbing to have clean tasting and clean smelling potable water all season. Make sure your water pump is working...and if not, rebuild or replace diaphragms and valves as necessary. Post launch: Test your toilet...make sure it's working correctly. Rinse ALL the antifreeze out of the system thoroughly with fresh water...but don't add any treatment to the tank until you're ready to use it. Put that down the head with the first "real" flush. Go over every inch of your boat with a fine-toothed comb. More boats have to be towed in, or find themselves back in the yard, in the spring than at any other time of year. And the owners all say the same thing: "I don't know what's wrong...it was working fine we put the boat away last fall."