Pick a flat, cemented surface

Avoid soil or loose gravelly areas

One each for the bodywork when wet/dry

Others for the mechanical bits

Additional rags for fork, chain, oil sump

Wet the bike/scooter from top to bottom

Avoid direct contact with electrical connectors

Diesel damages the paint’s finish

Auto-specific shampoos are best

Regular shampoos work at a pinch 

Clean every nook and cranny

Old toothbrush can be used

Separate cloth for mechanicals, bodywork

Layer of vaseline on chrome parts helps

Cleaning spokes a bit tiresome but worth the effort

Park the bike in a dry, shaded area

Make sure to place it under a cover