All bitches are different - some will have their first seasons very early at around 6 months & some are much later, as late as 18 months or more. At 8 months, your bitch could have her season at any time from now & the tell tale signs before a season include general moodiness & urinating more often. The Book Of The Bitch often mentioned on this forum is very informative on all aspects of a bitch's health including seasons so if you haven't already got this book, you will probably find it useful.
Jane