I have a gag plaque hanging on my boat. Engraved on a hinged brass plate is the statement: "For captain's use only." Lift it and underneath is another plaque that reads: "Port = left, starboard = right."
OK, I have that one figured out, but memory aids can be a great help, especially when it comes to lights at sea. Years ago, tired and exercising poor judgment, I almost turned into the path of a container ship because I misread the sequence of his masthead lights. Large ships (50 meters or longer) are required to carry two 225-degree white masthead (or range) lights. The forward one is lower than the aft, thus allowing you to determine the ship's direction. Before I get into the particular aid that helps me remember that fact, keep in mind that when you see the red and green running lights of a ship, it is already too close for comfort —
Possibly less than two miles away. Therefore, considering relative speeds and directions of approach, well, you don't want to do the math if it's coming your way.
The masthead lights cut you some slack, as they can usually be seen farther off. When you see a fixed white light on the horizon, there's a chance it could be a fishing vessel or a tug too far off for specialized lights to be determined. Or it could be a ship, also too far off for its range lights to be differentiated. Tugs and fishing vessels don't concern me as much as ships do. A ship could be running at 20 knots or more, and at first sight, I don't know the direction or speed. I'll begin taking bearings right away. If the bearings don't change much, it is getting closer. When that one white light becomes two, I know it's coming my way.
The night I almost became part of the cargo of that container ship, I goofed when I forgot the lower range light is forward. Afterward, I thought of my old pointer, Snoopy. She always ambled along with her nose to the ground — forward part lower. Now, when I see a ship at night, I think of Snoopy: forward light lower.
When you spot a ship at sea, if the lower light is to the left of the after light, it'll pass to your port; if the lower is to the right of the after, it'll pass to starboard. When those range lights are lined up — one above the other — the ship is coming your way. With apologies to the armchair captains who believe in strict adherence to the Rules of the Road, whether I am the burdened or stand-on vessel, I'm getting out of Dodge. Yes, I'm being a bit facetious here, but there have been a number of occasions when I've called large vessels to negotiate a passing arrangement, or just to let them know I'm out there, and I've encountered seriously English-challenged individuals. Therefore, I basically want to stay out of their way.
Among the other habits I've acquired is to compare the sequence and timing of observed navigational aids with those indicated on my chart. Changes in characteristics of lit buoys — especially those in a long channel leading inshore from a sea buoy — can be significant. For instance, a quick flashing light in a line of one or two second flashers may indicate a turn in a channel or a nearby obstruction.