If it's Italian threaded, both sides are clockwise. Which causes after use, but is simple.

If it's English, I learnt a nifty way of remembering. For pedals, remember "Back off." All pedals are reverse threaded on the left side, so if you turn either towards the rear wheel, it will come off. With English threaded cups, it's the exact opposite, "back on." So, when installing, turn both towards the back of the bike.

Simple, yes?