We maybe should start a new topic 'Heat detection'.
It's not easy. Heifers don't always mount each other. BH likes to run a couple of bullocks on, they usually do enjoy getting involved - but not always.
With house cows that you see every day, you get to learn her signs. (Hillie is hot, then fretful, then very soppy, then rampant.) But the first time is difficult if she's not a mounter or very vocal herself. If you can handle her in the field you may be able to learn how she reacts to a tail rub; this may change when she's bulling. Otherwise it's down to looking for the mucous and blood a few times, working out her repeat pattern, then getting her served the day before she bloods.
Otherwise I guess it's finding a suitable suitor in the flesh - not easy if you want rare breed pedigree.