1) The gears closest to the frame are the easiest gears, the inside gears are the easiest.
2) You can use the middle chainring for any speed riding but you only use the large chainring when going over 15 mph. This prevents cross chaining and allows a better cadence.
With a triple, you use only the smallest when going very slow as an option, going up hills, or riding on trails.
3) The three most important in real estate is location location location. The three most important words in bicycling is shifting shifting shifting. With shifting at the right times, you will go faster, ride further, and use less energy.
4) Pedaling should be easy. If you have to press down on the pedals, you are either going up an incline, going up a hill, or you are in the wrong gear and you need to shift. If it's not easy, you are in the wrong gear and you need to shift.
5) To shift to the bigger gears, use the big lever (aka brake lever). To shift to the smaller gears, use the little lever. Big gear, big lever; little gear, little lever.