How do I tell if my female is coming in season?
Estrus lasts approximately three weeks and for most dogs happens twice per year.  If you have an intact female, please look at the calendar of when she was last in heat when planning your class sessions.   When do they come in for the first time?  It depends.  Most start some time after 6 months to 1 year of age.  If you notice that she is being particularly fastidious about keeping herself clean, or your other dogs are paying a lot of attention to sniffing her or where she has urinated, that's usually the first sign that she is coming into season.  She may urinate more often.  Swelling of the vulva and bloody discharge soon follow.  This will be the first week.  Week 2, the discharge will thin and become more clear, but she is not out of the woods yet.  In fact, she is now ready to breed.  This is "standing heat" where she is most receptive and most attractive and can become pregnant.  You must be ultra careful to not leave her out unattended - where there's a will, there's a way.  Male dogs may scale your fence to get to her!  Avoid taking her for walks as you will leave a trail of scent that could lead potential suitors right to your front door.  The third week, the discharge may return and gradually the swelling and dripping will reduce.  She may be grouchy with other dogs while coming into heat and when going out.