‘Never leave milk sideways. Always stand it up!’
This is a rule in our house – it happens so often that the cap’s not quite perfectly on and there’s a slow leak… you don’t notice until a couple of hours later when your fridge has a milk puddle that goes everywhere and stinks, requiring a full fridge clean.
Unless you are very la-de-da and have a separate dunny, the role of the toilet lid when flushing can’t be over stated. Unless you enjoy having your child’s fecal matter all over your tooth brush, teach ’em young.
I have heard* that putting the lid down actually just creates a jet effect and the particles just get shot out between the seats at high speed, making no real difference to the overall amount floating around your bathroom. Not quite sure what the solution is, beyond “don’t think about it” or “rinse your toothbrush before using”.
(* from the series Bones, so it must be true. It’s got science in.)