From the top
Your Shagtastic Wash Pad/Love Glove/Muffy/Wash Pillow/Shagamittastic Mitt wash tool is now immersed in the bucket. Squeeze it while immersed in the suds, so she sucks up as much of the good wash water as possible. You start at the top of the car, commonly known as the roof, going from panel to panel working your way down. Once you have finished the panel, submerge and squeeze the wash tool into the Rinse bucket and rinse it by shaking it vigorously or gently dragging it across the Great Barrier Thingy, before placing it back into the wash suds bucket.
This method of rinsing the wash tool means you only have clean water going onto the car. (Check the rinse bucket water colour out after the wash is done to get an idea of this, you'll never wash with one bucket ever again!) Gather as much water and suds as your mitt can carry, then re-apply to the next panel. Repeat this process, washing every panel on the car. Doing it this way means you are never putting dirty water onto your car.
The reason you start at the top is to minimise contamination of the Rinse bucket. The lower the panel is on the car, the more it collects road grime. So always wash the lower and rear panels last. Its also good practise to use twice the amount of suds as you would on the top sections when you're doing them, as well as turning the wash tool over often for each pass or wipe of these areas. Again this is all done to minimise the chance of ever micro scratching your paint.