every bitch is differnet, they say from 6 months, to check/ keep an eye on them.
but some can go to 18 months before a 1st season.
as colin had said
signs to watch for,
increased urination, swelling of her lady bits, spotting of blood,licking of her lady bits, some become more clingy, so start doing a daily wipe with a white tissue so you can watch for any change, blood streaks, ect.
my bitches have all been differnet, strating at 6months, 71/2 months,8 months, one went to a year, all normal, they now all seem to come in heat together
.
try not to worry, she will come into season, when she is ready, there is no right or wrong time to have a 1st season.
just keep an eye on her.