One thing we learned to do from a very respected cattleman, was to get the heifers in an alleyway so you can see their behinds (we do this with each individual) and look to see if we can see the start of an udder. Of course that was back when there weren't EPD's and doing this helped to eliminate heifers that weren't going to be good milkers. FWIW
If you have a lot of heifers that could be time consuming.
There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.