how know the bitch is getting heat

Question
i am jinto from bangalore i have around 12 dogs including bitches.......i'm a seminarian, ...i want to that how i can know that my bitches are getting heat?....when i want mate her with male dog....how i can sell the puppies???....what the normal rate of the puppies.....my dogs are 1.labrador[both brown and white],great dane,german shepherd,lhaso apso.....

                            i think i will get a specific answer about all my question...thank you..............

Answer
First you want to separate the breeds.  The last thing you want is a Great Dane Lhaso Apso mix.  

Keeping the females together you get a dorm effect, when one comes in, the others will follow. You'll notice that the females start to get "antsy" and more aggressive, then they will go into heat.

Depending on your demographics and breeds you choice to breed will directly affect the price someone is willing to pay.  But before you even consider breeding, you want to ensure that these pups have good homes and the breeding dogs are in top physical and mental shape.  If you are breeding just to make money or "puppy milling", with no regard to the future of the dogs or their potentially thousands of off-spring,  do the world and the dogs a favor and have them all fixed.