• Before installing new equipment read the instruction manual from cover to cover and highlight information of particular interest or importance with a hi-liter pen
  
  
• Don't be shy about calling customer support if needed. Furuno, ICOM, and Simrad (among a few others) have noted positive track records in customer service. This is part of what you pay for with a slightly more expensive device but it can be worth its weight in gold when you need it.
  
  
• "High and Dry" is key - Try to keep the installation out of the bilge, and away from batteries, fuel lines and direct sun light, if possible.
  
  
• Magnetic fields cause interference. Stay clear of bilge pumps, battery chargers, windshield wiper motors or anything else with an electric motor or permanent magnets in it.
  
  
• Do not loop or "spool" wires, especially antennae transmission lines (coax) or data wires (like the NEMA wires from device to device) because loops can radiate concentrated magnetic fields.
  
  
• No matter how small the current draw (amps), don't go smaller than 16 AWG wire, unless it's what the manufacturer recommends.
  
  
• Take your time and do a good job.

Damian also pointed out that the ABYC specifically recommends against soldering connections. Good marine-grade crimps and adhesive shrink tubing are the preferred way to connect wires in boats.

If they get too hot from being left in the sun, the internal pressure can build up enough to pop the case apart . We had this happen to both a sonar unit and a handheld GPS. This is NOT covered under most warranties! The lesson: try to locate electronics where they can get some shade in really hot weather, or be prepared to cover them with a wet towel.

Cable clams have made it easy to add or remove devices that require cable runs through bulkheads, such as transducers, antennas, power cables, etc.