If leading a spot card and wanting to give count, the lowest card was led from an odd number of cards and the third best was led from an even number of cards; if leading from a worthless holding and not wanting to give count, the highest card you could afford was led.
When leading a spot card with the intention of giving count, the lowest card is led from an odd number of cards, and the third best is led from an even number of cards; if leading without giving count from a weak hand, lead the highest affordable card.