I explored ways to find the lowest Wh/km and found that what matters most is starting from stop. We have a very heavy car. Model S is more than 2 tons, X is even heavier. Starting from stop uses most energy. That's why you waste a lot in stop and go traffic. If you can be gentle on this, your figures will look a lot better. If I keep the motor output at around 50kW when starting from stop, I already beat most ICE at traffic lights. And it seems my car also find this value gentle enough, you may consider doing the same if you are energy conscious.
There are times when I needed to keep the motor output at 200kW to overtake highway traffic, effect on Wh/km is not too obvious, perhaps the time at 200kW was too short
Another point is constant speed, I know how good it feels to accelerate and brake and accelerate especially on highways in a Tesla, but it hurts your Wh/km SO much. With constant speed, you can make use of the inertia and keep the car's heavy weight on our side
Regen, make good use of it, step on the brake pedal when your speed is around 10 / 20, it helps a lot
Hill doesn't cause too much trouble. As many has pointed out above, you will regen on the way down. But I noticed the car regen more at higher speed when going down (don't know why) compared with slowing down before or when coming down, so try not to slow down
Air-con, effect not apparent when comparing summer with winter values. Probably I use some energy warming the battery in winter and some energy to run the air-con in summer
Tyre pressure, don't forget getting it right even we don't need to visit gas stations now