Assuming that what you have are pullets (girls), one thing to look for is comb/wattle development. Young birds have yellowish to pinkish, undeveloped wattles and combs, these get larger and turn blood red at about the time the pullet reaches Point of Lay. The comb size and shape varies quite a bit depending on breed, but the red color pretty much signals maturity, so when you see that, you know egg laying isn't far off.
