First and foremost, be sure that your bitch is both physically and mentally mature enough to be bred. Just being in heat is NOT enough to warrant a breeding. A general rule of thumb is 2nd heat or 15 months but this can vary by breed or individual. I suggest you consult with your vet.
Next, your bitch will likely show signs of being swollen in the vulva. Most females have their first heat cycles at around 9 months of age but can be as early as 6 months. Watch for this and mark your calendar, this will help but not guarantee, you a good heads up for next time. Mark the first day of swelling as day 1, first day of red blood will work if you don't know this date.
Once swelling has begun, begin swabbing your females vulva once or twice daily with a clean, soft cotton rag, a paper towel will do and is also disposable but it's nicer if it's dampened with a little warm water first.
Don't be shy. - You may need to insert the top 1/4 of your finger or so to get to any discharge, use a disposable medical type glove, which you can get from any chemist's.
If the blood is red, she's just started, most females will average 9 - 10 days before they are ready to breed after this sign but every bitch varies, some are quicker, some muuuuucccchhhhh later...
Keep monitoring the colour of the blood/discharge daily, once this becomes a straw colour, she is ready.
About this time, you should also start seeing other signs such as flagging (putting tail up and pushing her bum towards anyone/anything she thinks may be able to help her out.) She will likely act more flirtatious and silly. Other bitches may treat her coldly due to the wolf mentality of only alpha bitches being allowed to have pups. Many bitches will also appear to be urinating more often but usually this is just them trying to mark their trail for a willing mate to find them.
Remember that although a WHFT is generally an excellent bearer and mother to her puppies things sometimes don't go to plan and you should ensure you have the finances to cover any medical cover that maybe needed by either the bitch or her puppies.
Ensure you have loving and well vetted homes before you breed your bitch, we have a waiting list of vetted potential owners who want a Delwires puppy, which is guaranteed to be below the breed average for inbreeding and thus help to minimise any genetic faults occurring.
Tips & Warnings
Some bitches have 'silent' heats, sorry to those of you out there with this issue, best to have a leashed dog to test her with, in this case. If you breed too late in the heat cycle after she's ready for a mate, you will get very small litters as a norm so if you’re serious, you will just need to be more studious of your bitch.
Knowing your bitches normal behaviour with and without other dogs present both inside and outside, you should be able to pick up on even the most silent of heat cycles.