30 Personal Finance Rules of Thumb...

I like this one.
 
so you should buy a second hand 4 door car on the last day of the month, from the youngest dealer spending a maximum of half your gross salary, not paying the asking price, keeping it for at least 10 years, washing it before getting it serviced at the end of April while running it on a 15% ethanol blend and only buying petrol when the temperature exceeds 15C.

makes sense.