Every year, or at relaunch each spring, swing your steering compass and reinitialize your fluxgate compasses to ensure that they're in full working order and properly compensated.
Check for the proper alignment of your compass with the fore-and-aft axis of the vessel.
Check for magnetic interference from a variety of sources, including, but not limited to, tools or knives near the pedestal, portable speakers or VHF radios near the compass, steering-wheel spokes, dodger brackets, air horns, propane tanks, anchors, and other large metal objects. For remotely mounted fluxgate compasses, make sure that nothing magnetic is in the area and that your crewmembers know the location of the remote compass mount.
Check electronics and how they relate to the compass. Check your compasses with the radar on/off, with the wipers on/off, with the SSB transmitting on various frequencies or idle, with the engine on/off, and so forth.
While under way, periodically check the compass against celestial bodies or known landmarks.
If the compass develops air bubbles or other problems, fix them immediately to avoid more problems later.
Wash the binnacle compass in fresh water and cover it when not in use to preserve the clarity of the glass dome.
Carry spare lightbulbs of the correct voltage and color so that replacement is easy.
Carry spare chemical light sticks and/or flashlights and batteries for illuminating the compass in the event of an electrical failure.