Arrange the rocks into a loose open pattern. Direct one water jet, like the filter exhaust, along one side of the tank. Aim it slightly inward so that the water spins in a slow vortex. Add a power head as necessary. Water should be moving through the entire aquarium so the live rock and sand can filter it biologically. This keeps biological material from building up, and it keeps food suspended so the fish will have plenty of time to consume it. Saltwater fish, unlike freshwater fish, are generally used to keeping position in waves and are not upset by vigorous water movement. This removes undesirable material, including suspended algae, from the water so it does not dirty the water as it rots. While replacing a mechanical-filter cartridge more often might also be a good idea, a big protein skimmer is perhaps even more effective in removing organic sludge. Adding the skimmer air line will change the water level in the skimmer. Be prepared to adjust the skimmer so the water doesn't rise too high and spill out of the aquarium. The size of the skimmer will vary depending on the size of your tank. For example, a 60 gallon (227.1L) skimmer will work on a 29 gallon (109.8L) nano-reef. A magnet cleaner has two parts, one piece on the inside of the tank and one on the outside of the glass. As you move the outside piece, the inside piece moves and cleans the glass. This tool will allow you to do quick daily glass cleaning without putting your arm in your tank. This works best if the lights are not extremely bright so the glass will have little coralline algae on it. This will greatly reduces the risk of heater breakage. Heater capacity should be on the low side because the lights and pumps create some heat. Low temperatures from a cold house or insufficient heater capacity are less likely to kill the fish than excessive temperatures from a powerful heater.
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One-sentence summary -- Use a circulator to move the water vigorously throughout the tank. Put a protein skimmer on your tank. Clean the glass with a magnetic cleaner from the outside. Buy a heater that has a solid, plastic body.

This doesn't just apply to saltwater adventures, but to fresh water outings as well. If you have an older motor or one based upon an older design, you should buy a set of flushing "earmuffs": two flexible rubber seals attached to a metal clamp. One side can be attached to a garden hose, while the other is solid and will serve to plug a water intake. Slip the apparatus onto the lower unit where the water is taken in and then attach the earmuff to a garden hose. If there are additional water intakes that are not covered by the earmuffs, use duct tape to cover them. Attach a garden hose to the earmuffs or mount and turn the water on. Newer motor designs already have mounts, and so the earmuffs are unnecessary. Start up the engine. The water pump will then flush out the system. (Practice safe boating and remember to stay clear of the prop and keep the motor out of gear.) Carefully put your finger through the stream of water exiting the motor. It should be warm, but not hot. If the output is not strong, you may have some debris stuck in the outflow tube. Immediately shut down the engine to prevent overheating and damage. If the flow tube is obstructed, insert a small piece of wire into the tube and work it back and forth (again, while the engine remains off). Start the engine again and check the output. If that doesn't solve the problem, you may need a new water pump impeller. Disconnect the fuel line if the boat is going to be stored for an extended period of time. You should allow the engine to burn the small amount of fuel that is in the carburetor. Old fuel can gum up an engine, and the best way to keep the motor running at a high level is to burn off all fuel remaining in the mechanism. Be advised that if you own a two-stroke motor with more than one carburetor, the top carburetor will run dry first while all of the cylinders will continue to run. Without fuel, the top cylinder will not be getting any lubrication. Listen closely as the engine may get louder as the top cylinder begins to overheat. Also beware of any burning smell that is unusual for your engine. Just to make sure that all the moving parts are going to stay put for the next few minutes of cleaning. There should be no water or other liquids moving freely about the engine compartment. If you find leaks, consult a boating mechanic. Some of the best options are lubricants such as WD-40 or Quick-lube. Be sure to lubricate or grease all the moving parts such as the pivots, shift mechanism, throttle cables, carburetor valves, etc. Clean it off, and then cover the whole motor in a canvas or plastic covering for the duration of storage.
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One-sentence summary --
Flush out the engine at home after every outing. While flushing the motor, check the water pump to make sure it has good water flow. After flushing the engine, disconnect the fuel line (if applicable). Be sure to turn off the key and, if you have a battery switch, turn it off. Take the engine cowling off and check for fuel or water leaks. Wipe down and spray all accessible mechanical components and moving parts with an anti-corrosive. Place the cowling back onto its fittings.