Drive it like a locomotive engine. Accelerate and attain a decent speed. then maintain that speed by taking your foot off and on, on the gas pedal.
In my opinion all cars have two speeds at which fuel efficiency is maximum. one below fifty kmph and one in between 80 to 110 kmph. try to drive at near those speeds.
taking the foot off the accelerator in A/T cars, maybe not the ones with CVT, make the cars go neutral. and make the RPM of the engine drop. this is a big advantage.
do not accelerate hard.
break as little as possible and try to not to loose the speed at which you are going. conserve the energy in other words. Similarly, do not accelerate to speeds which you cannot maintain for long.
when in slow and crowded traffic, go a little over the average speed of the traffic. if you drive at the average speed you ll utilize as much fuel as everyone else. if you drive fast you will not be able to maintain the speed and ur car will consume more fuel.
All the above tips work for me and I am a driver that is obsessed with getting more Kms out of my CNG tank and drive an A/T car.