A very thoughtful & useful thread!
Just in case I'll add this if it's OK....
If using normal tap water, simply just doing a water change to bring the Ammonia etc. levels down is not always a safe thing to do and could lead the beginner to much confusion when he or she sees the levels possibly rise!
We all know that water must be dechlorinated. Water contains Chlorine (Cl) and / or Chloramine (NH2Cl) that is used to kill bacteria in the water, i.e. will also kill filter bacteria. Should the water contain chloramine, the action of some dechlorinators will produce Ammonia! Some of the dechorlinators also bind this ammonia into safe ammonium (that can also be consumed by the filter bacteria). The levels of Ammonia are usually small, but the quality of water can change (the amount of Chlorine / Chloramine added), hence I recommend testing the dechlorinated for toxic levels of Ammonia water BEFORE it goes into the tank!
I then recommend testing your tap water for levels of Ammonia BEFORE putting it in the tank.
Note: Dropper test kits simultaneously test for levels of Ammonia (toxic) and Ammonium (safe). This is why they are labelled NH2/NH3... These two chemicals are in balance, the percentage of the ppm (mg/l) result is related to the pH of the water (and to a lesser extent the temperature). The higher the pH, the higher the percentage of toxic ammonia exists.
Andy