The trim is only a factor in that you probably would like to have the aircraft trimmed for hands off flying. Thus the trim setting will provide hands off flying at a further aft C of G, if you choose to fly that way, and can arrange loading that way. This will be a small factor in endurance, probably too small to notice in a 172, but worth a try. The aft C of G reduces drag in any conventional airplane, as the horizontal stabilizer does not have to lift down as much - in any stable, normal flying, the horizontal stabilizer of a GA plane never lifts up. The undercarriage configuration is not a factor in range nor endurance, other than to say that if you have converted a tricycle plane to be a taildragger, then yes, it will have less drag, and more range and endurance.
Otherwise, as said, flying a suitably slow speed (known as the "bottom of the bucket" on a power curve chart), and lean according to the engine operation manual are your best means of achieving best endurance.
Understanding these principles is important for pilot skills and understanding, but for recreational flying in a GA plane there will will likely only be two occasions when you will put this to practice: If an examiner asks you to set up for it, to prove you understand, or you have to hold for improving weather or some other delaying situation. There is a close relationship to realizing that you are low on fuel, and may not make it to any destination, but this would still be flight for best range, rather than endurance, but it demands similar discipline. Once, with 300 miles to go, a steadily increasing headwind, and zero airports between me and the fuel airport, I sure optimized my range and fuel use, and made it - just. Failing to optimize fuel and range, and I would have landed short for sure.
One other factor I employ if I'm planning a long trip, is a wash and wax of the whole plane, that's good for a couple of free knots of cruise speed, and I've never heard of an owner complaining if you offer to was and wax their plane!