When the moon forms a crescent with the horns directed toward the sinister (i.e. left), it is waxing (i.e. getting bigger).
One way to tell whether the moon is waxing or waning is to hold up your hands in front of you, with the thumb and fingers curled like the letter 'C'. (Imagine holding a big sandwich you're about to bite into.) When the moon is waxing, it's shaped like your right hand; when it's waning, it's shaped like your left. (It crosses my mind that I'm not sure whether this is true in the southern hemisphere or not.)
There is, however, an easier way to tell. The moon rises about one hour later each day. (In a 29 day lunar cycle, the moon rises 28 times.)
The new moon rises at sunrise and sets at sunset. Then, for the next week, the waxing crescent is visible in the west in the evening sky. At the first quarter, the moon sets at midnight. After that, the waxing gibbous moon is up most of the night, until it's full, at which point it rises at sunset and sets at sunrise.
The waning moon rises sometime after sunset and sets sometime after sunrise. At the third quarter, it rises at midnight and sets at noon. And so on, until it's new again.
So, if you see a crescent moon near sunset, it's waxing, and if you see one near sunrise, it's waning. (If you're not sure whether the time is closer to sunset or sunrise, then you probably have other things to worry about than what phase the moon is in.)
Finally, I have to observe that, a hundred years ago, this writeup probably would have been about as informative as "the sun rises in the morning and sets in the evening."
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