IF you are looking down on the nut as you turn it, counter clockwise is lean. Or the other way to think of it; screwing the jet up into the carb=lean, out=rich, not different from a faucet (the water in this case being the gas).
In case you dont know there is (if yours is like mine) a little button on the side which helps determine the mixture. It is on the side and pushed upwards. If the mixure is to rich, pushing the button will lean it a pinch and increase the idle. It will slow down if the mixture is already lean. The trick however is pushing the button just far enough because it will bog out, rich or lean if you push it to far. Thus the button is better for detecting a rich mixture.
Dave