seeing as though noones replied ill just tell you what i do.
1. make sure the car isnt too hot so you dont burn yourself if you come into contact with it. and make sure its off!!!
2. undo your radiator cap.
3. there will be a screw on the right hand side of the bottom of the radiator (looking at the engine bay). undo that, make sure you dont lose the rubber washer between the screw and the radiator. this will make all of the water rush out.
WATCH OUT, IT WILL COME OUT PRETTY HARD.
4. put the screw back in, then fill up with clean tap water then put the rad cap back on.
5. run your car for around 1min. then turn it off.
6. repeat steps 2-5 till the water comes out clean when its being drained.
i use the nulon coolant that you have to mix yourself. i use a 50/50 mixture of distilled water/coolant.
hope that helps.