In general dogs are normally in heat about 3 weeks. The first week they have a red discharge then the second a clear or straw colored discharge then almost no discharge the last week. They usually breed sometime in the middle of their heat usually in the range of 9-14 days of their heat season.
Dogs are individuals so you have to see when the female is agreeable as there is no one specific day for sure. Heat cycles can vary in length for an individual also.
One sign of her being ready would be for her to 'flag' or roll her tail to one side when touched on her hind quarters.
With your constraints on wanting to get the timing right I'd suggest doing progesterone testing.
http://www.peteducation.com/article.cfm?c=2+2109&aid=3201
Using a kit like this one
http://www.pinnaclepetsupply.com/premate.htm
or another some breeders test at home but a vet can check it for you.
http://www.hilltopanimalhospital.com/modern%20breeding%20management.htm
If your vet is unfamiliar with this or has to send out to get testing done which takes 2 - 3 days then you may want to work with a vet specializing in reproduction
http://www.whelpwise.com/testing/veterinarian-links.html
http://www.therio.org/search.cfm usually I change name to work state to search by state.
I find the best test is a proven stud dog as they usually know when the time is right but barring that the vet tests can work too.
Hope this helps you!
Sorry for the delay I was offline for a little bit.
As you are not sure of her ovulation time going early may be better than going late.
But your girl should not be locked with the male the whole time. They should be introduced to see if she is ready and he is willing. Then they should be controlled for breeding times as you will want to know what day she breeds with him to time litter arrival better.
Call your vet and see what they charge to do an ovulation timing test.
Dog Expert:Rescue, Train,Breed,Care
30+ yrs dog home vet care & nursing, rescue, behavior&training, responsible show breeding, genetics