Dispose of the used coolant in a used coolant-holding tank to be picked up with the used oil for disposal. Never pour the used coolant down the drain. Ethylene glycol antifreeze is an extremely toxic chemical. Disposing of it into the sewer system or the ground water can contaminate the local environment.
To avoid injury do not remove the surge tank cap while the engine and the radiator are hot. Scalding fluid and steam may be blown out under pressure.
Tip:
It is preferable to use a cooling system cleaning product before following this procedures? it will give the best results for the flush process.
1- Place a pan below the vehicle to catch the draining coolant.
2- Remove the reservoir cap.
3- Run the engine until the thermostat opens. You can tell the thermostat is open when both radiator hoses are hot to the touch.
4- Turn off the engine.
5- Take off the little hose going from the top of the top of the radiator to the reservoir - marked in red in the pic - take off the reservoir end only.

6- open the dran plug on the radiator to drain the coolant in it then put the plug back on
7- Turn on the engine and keep it revving at 2,000 RPM.
8- Old coolant will come out of the little hose; replace draining coolant by pouring fresh water into the reservoir. Note that the water level in the reservoir should not go lower than the MIN mark.
9- Keep on doing this till the coolant coming out of the hose is perfectly clean.
10- Now replace fresh water with new coolant until the cooling system is filled with new coolant. You will now that the system is full with coolant when the hose drips clean coolant rather than fresh water (watch for the color of the fluid coming out of the hose).
11- Let the engine rev at the normal idling speed.
12- Put the hose back on the reservoir.
13- Fill with coolant to the MAX mark.
14- Put the reservoir cap back on.
15- Keep the engine running till the cooling fans kick on then back off again.
16- Very carfully and i repeat very carfully open the reservoir cap to let out the air accumilated on top of the coolant. that air was traped in the system during the flush and was bled out buy the normal cooling system operation, you will notice that the more you open the cap the higher the coolan goes so you don't need to take off the cap, just unscrew it a little and keep an eye on the coolant level so that it doesn't spill then tighten it back on.
17- Repeat step 16 again after the cooling fans kick on then back off to conclud the bleeding process.
18- Fill with coolant if needed and check for leaks.
Notes:
No need for additional bleeding procedure for the cooling system; our systems are self-bleed systems and steps 16 and 17 makes sure that the process is done right.
The engine cooling system will not take as much coolant as stated in the vehicle?s manual; this is because there is still some fresh water in the system around the engine block area.
MMamdouh
***EDIT***
Today I did a coolant flush to my car and I would like to share this couple of ideas:
*) Some people were asking why the manual says the engine takes 7 liters of coolant whereas it used some 4 liters only during the flush; the answer is that some 3 liters of water are still trapped inside the engine block.
Today I tried to drain this amount of water as well so I put back the little hose into the reservoir and removed the drain plug and with the engine off I blowed into the reservoir (through the cap hole) and the water started blasting out of the drain plug, by the amount of coolant I needed to fill the system I say I drained an extra liter of water... is it worth the effort or not? You decide on that.
*) After almost 7 years of hard work my reservoir was full of deposits from the inside and it was dim and ugly looking, I tried to put some water and washing machine soap but that was not effective, I then tried a tooth brush... it worked fine for the accessible parts but their is more inaccessible parts on this reservoir that anything else.
My neighbor suggested a really strange thing... he told me to put a handful of sand and some water then shake the thing like hell

I was skeptical at first but after I tried that it I can say it is effective as hell.
It is practically like using a wet state sand paper to scrub all the interior deposits... my reservoir is not as good as new. Needles to say you need to wash the thing very well after a sand shower and don't use anything but sand... dust or mud won't work at all just pure sand with water, a little soap can be of some help.
MMamdouh