Lots of residential and commercial sites, lighting is one of the major consumers of electricity. The most common types of lights used in homes and offices today are: 
Incandescent Bulbs: most commonly used, cheap to buy, generate lot of heat, inefficient and high energy consumption.
Fluorescent Lights: More commonly known as the 'tube lights'. These are longer lasting than incandescent and consume less electricity.
Compact Fluorescent Lighting (CFL): commonly known as 'energy savers'. These consume much less power compared to both fluorescent and incandescent lights, and they last up to 6 times longer than incandescent bulbs.
This table shows how you can replace the existing incandescent bulbs with the CFLs:

Incandescent	40W	60W	75W	100W
Compact Fluorescent	8W	11W	14W	18W

This shows that a 60W incandescent light bulb can be replaced by an 11W CFL. Generally, aa CFL lasts around 7000-8000 hours compared to a normal globe, which lasts around 1000 hours. Replacing a 60W bulb with an 11W CFL will save you: Savings = [0.06 x 0.011] kW X 8hrs/day X 30days/month X 20.59c per kWh = $2.42 per month.
Through these savings, you will recover the cost of buying the CFL in about 3 - 4 months.
 Energy Efficiency Measures
 Replace incandescent bulbs with CFLs.
Do not leave the lights on unnecessarily. If the room is unoccupied and the light does not need to be on, then switch it off.
Try to use task lighting if possible. This is where instead of lighting the entire area, you only light up the specific working area. For example, lighting up your desk only when studying.
The common cheap fluorescent light fittings have magnetic ballasts, which generate a lot of heat, cause the flickering and the annoying sound you hear when the light gets a bit old. Use fluorescent fittings with electronic ballasts, which will consume less electricity, remove the flicker and noise, emit less heat, and last longer.
Replace the normal tubes in fluorescent fittings with Triphosphor tubes. These last longer, emit 20-40% more light than standard tubes and have a much higher Colour Rendering Index (CRI).
Triphosphor tubes can be used for delamping, whereby, 2 standard fluorescent tubes can be replaced by 1 triphosphor fluorescent tube.