1)Avoid reving your engine above 3500 rpm.
2)Avoid sudden acceleration.
3)Avoid sudden braking.
4)Avoid using the air con.
5)Pump petrol @ JB & tilt your car sideways when you
pump.Imagine the theory of pouring beer into the mug.
6)Install some accessories to improve your throttle response so
that you need to step less on the throttle to achieve desired
speed. Voltage stabilizers, grounding cables & aftermarket drop
in filters help.Fuel magnets do not help.
7)Inflate your tyres slightly above the your average pressure.I
pump 220kpa. Used to pump 200kpa.
Avoid overloading your car with unecessary
weight.(this is the most important)
9)Watch out for poor quality sport rims.Heavy sport rims adds extra
load to your engine.
10)Plan your route to avoid jams.Moving off a stationary vehicle
saps the most fuel.
Hope these tips helps. 