I tried searching for similar thread here but wala ko kita so I'm creating one.
Got this from another forum:
1. Aggressive driving this is a NO-NO (rapid acceleration and braking) sources said you can save 30% of gas if you avoid this. also its muchs safer for you and your passenger.
I say pa-tanggal nyo na yung mga tingga sa paa nyo and replace it with Helium.. 
2. Observe Speed Limit!! - certain cars have different speed limit but ussually gas mileage usually decreases rapidly at speeds above 96kmh.
so kung hindi ka hinahabol ng CARJACKERS wag na lang sayang ang miles ..
3. Remove Excess Weight - Oh my that subwoofer will have to go!!
Avoid keeping unnecessary items in your car, especially heavy ones. An extra 100 pounds in your vehicle could reduce your Km/L by up to 2%. The reduction is based on the percentage of extra weight relative to the vehicle's weight and affects smaller vehicles more than larger ones.
hehehe tell your GF/WIFE to lose weight hahaha natawa ka?
ikaw din magreduce ka na!!!
4. Avoid Excessive Idling - Idling gets 0 Km per Liter. if you have to wait for more than minute switch off that engine :P,
and dont DO IT sa car!! :P mahal na ang GAS!! =))
baka paglabas ng anak mo may TAG na Made in HONDA =))
5. Keep Your Engine Properly Tuned - Fixing a serious engine problem, such as a faulty oxygen sensor, can improve your mileage by as much as 40 percent.
Wow!! 40% pwede na yan masasave mo dyan to avoid excessive idling 
6. Check & Replace Air Filters Regularly - Replacing a clogged air filter can improve your car's gas mileage by as much as 10 percent.
hehehe baka may kamote na yan linisin na yan!!
7. Keep Tires Properly Inflated - You can improve your gas mileage by around 3.3 percent by keeping your tires inflated to the proper pressure. Under-inflated tires can lower gas mileage by 0.4 percent for every 1 psi drop in pressure of all four tires. Properly inflated tires are safer and last longer.
Traction!-Traction! underinflating!! hello papunta ka sa office hindi ka kakarera!! tamang pressure lang..
8. Use the Recommended Grade of Motor Oil - You can improve your gas mileage by 1-2 percent by using the manufacturer's recommended grade of motor oil. For example, using 10W-30 motor oil in an engine designed to use 5W-30 can lower your gas mileage by 1-2 percent. Using 5W-30 in an engine designed for 5W-20 can lower your gas mileage by 1-1.5 percent.
so stop using race car oil on a daily car lol :P
9. Planning and Combining Trips - Combining errands into one trip saves you time and money. Several short trips taken from a cold start can use twice as much fuel as a longer multipurpose trip covering the same distance when the engine is warm. Trip planning ensures that traveling is done when the engine is warmed-up and efficient.
With a little planning, you can avoid retracing your route and reduce the distance you travel as well. You'll not only save fuel, but also reduce wear and tear on your car.
kaya pag nag GF ka dont choose North and South dapat South and South 
10. if all else fails buy a Jazz or City hehehehehe
Kamo unsay tips ninyo?
BTW, I'm driving a '95 Honda Accord.
Fuel Displacemet: 2.0
Average Fuel Consumption: 1L:5kms (Waaahhh!!!)
17" mags
Naka-muffler
Matic
Unsaon ni para maka 1L:10kms ko? Huhuhu... Kaya ba?
******