Well, if she is bawling and wagging her tale a lot, humping other does.... Also if you take a buck rag to her and she has all those signs then she's in heat. What kind of goat? There are seasonal breeders and then there is year around breeders.
Oh, when I had my buck in with my does, I couldn't tell unless he was humping one of them. Chances are if you leave them together for a month or two she will take. Does he smell "Bucky"? That is also a good indication that he is in rut, and ready to breed. Is he also boar?