Never rely on one source for determining your position.
Always study the charts for your journey with great care before departing. Check your position regularly. Double check the waypoints before and after inputting them into the GPS.
Never pass a significant landmark without checking it on your chart. Having lots of electronic navigation equipment is not an excuse for lack of knowledge or lazy navigation.
Square or rectangular shaped pencils are better for navigation, as they don’t roll away.
Prior to entering a new port, you must carry out as much research as possible. As well as books and manuals, if there is local knowledge available, seek it out. If the port is nearby to your present location and the opportunity arises to visit that port via land, grab this opportunity to view the entrance. It will provide you with some very useful information.
If you arrive at a new port at night, stand-off and wait for dawn before entering (unless it is a major port that you know well, it is well marked, charted accurately and your charts are up to date). A few hours of boredom is worth the wait. Bar entrances can be particularly lethal.
Fixing your position can be done several ways besides using your GPS. Batteries can fail and GPSs can break and have errors. Have some handy position fixing tricks up your sleeve.
To take a fix, always note the time the fix was taken. This is imperative for DR (Deduced Reckoning). It is fun to experiment with different ways to check your position, especially when coastal cruising.
If you have reciprocal dyslexia, an easy way to calculate the reciprocal bearing is to plus or minus 200, then adjust by twenty accordingly. For example, for the reciprocal of 050°, add 200° = 250°, then just minus 20° = 230°.
Safe Water (Navigation)
At all times know where your safe water is (i.e. good depth, no obstructions), for emergency collision avoidance or giving room to the stand on vessel. This is very important in busy waterways.
We sometimes break up long sea journeys by taking star sights. It is good practice and very satisfying to find your position by the stars. It also provides the confidence to know you can get home if all else fails. Practice celestial navigation prior to your voyage and take all your books and equipment on board. A celestial computer is a great aid and speeds up the whole process, however they are prone to inherent failures of electronic equipment (usually a flat battery and loss of data).