That is not exactly what happens. See, unlike humans, dogs don't have crushes or anything like that. The female dog goes into heat, and the male dogs smell it and know they are supposed to mate with the girl dog. The boy dog then mates with the girl dog, and usually it is successful and they have puppies.
I don't know, it depends on your opinion really, most girls like having boy dogs but some like to have girls but the boys like to have girl dogs so it is merely your own decision!
The girl puppies will start acting strange then the boy dogys will start to follow them  and the girl dogs whine and the boy dogs grunt so that's how u know
i don't know but i do know you need to have a boy and a girl that's not fixed
By asking him.
boy dogs are usualy louder but girl dogs can be quite sleepy
the girls have nothing on their stomach but boy dogs have something hanging there, i know its gross, but that's how you tell
The boy always has to aks the girl
Gorillas have the same resproductive system as humans, dogs, horses and other mammals. To know whether a gorilla is a boy or girl just look at their reproductive parts.
Justin bieber he has two dogs a boy and a girl
Im sure you mean why do boy dogs lift a leg and girl dogs don't. Well, the answer would be because if boy dogs tried to "go" without lifting their leg up they would just end up peeing on their leg. and somehow they know that they dont want that.
Shep is a girl
Ashley Tisdale Has 2 Dogs 1 Dog Is Named Blondie And Blondie Is A Girl And Her Other Dog Is Named Maui And I Don't Know If It's A Boy Or A Girl