How to flush radiator

What is the proper way to flush the radiator? Its about time for me to change my radiator fluid, but I'm not sure how to flush out the complete system.

there is a small plastic plug on the bottem of the radiator. Unscrew the Cap before unscrewing the plastic plug.

Yea, I have figured out that much, but wont that just drain the fluid that is in the radiator? Not the fluid that is still in the lines.

well, yeah, it wont.
drain it, fill it with water & radiator cleaner, turn the fans and heat up to high, and let it run for 15 mins. flush it and fill it.

Only use cleaner if your having nasty gunked up coolant, other wise, its not needed. Just flush it with water a couple of times and drain it.