First start by cleaning the top of the frame give it a good scrub until your water runs clear.
Then clean down the window in a side to side motion until you reach the bottom of the window.
Then remove the brush from the window and place it at the top of right of the window and move it across the window in an up and down movement when you reach the left side of the window remove the brush and rinse down the window in a side to side movement then give the sills a brush.
Kev