
With the first time you don't know when it is likely to happen as it can be from 5 months to 18 months or later,put light coloured bedding where they sleep over night and check it each morning, during the day they tend to keep themselves clean so you don't see any discharge.
I have a male who does " wee tasting " about a week before the girls come into season so from then on they get dabbed with a white tissue each morning before they have a wee to check for bleeding which happens before any significant swelling with my lot.
My girls hump each other or the boys leading up to coming into season.
I tried sending my male Rhuari to stay at my Mum's, his whining under his breath and hunger strike was more than she could stand so he arrived back after a week.
Now for the past 4yrs.the girls wear hygiene panties and when I can't physically watch them one or other is crated up off the ground away from visiting suitors. The males have vanilla extract[not essence] smeared on their noses and chests to detract from the scent the females give off[ tried other things including things meant to be used and they didn't work].
The more humans there are in the home the more chance that someone makes a mistake and allows the 2 of them to get together, I live alone so only me to blame if there was an OOPs mating.
Any neuter/spay needs to wait till the puppy has finished growing as those hormones influence more than just reproduction.
Good Luck.