Well, I try to make sure they are fed, so they're not concentrating too heavily on "foraging" for food, etc...I have a tank pre-set up with several bushy plants, and during the morning/afternoon, I take the male out from the rest of the colony, and place him in the set-up/breeding tank by himself, and I will wait til the "FOLLOWING" evening, before placing the female in with him, and let nature do the rest, lol...
However, I tend to be impatient at times, and when I don't isolate the male by himself long enough, he doesnt do the persistent calling ;o( So, with a lil patience, things usually go a LOT better, as far as breeding. In the past 2 weeks, I had a VERY successful X. borealis breeding (over 225 tads hatched, and still doing great) And this morning, all the tads from the albino male/retic female, are hatched (there's around 90 or so tads), but it was such a short spawning, the male let go, about an hour or so into the breeding ;o( But at least I have some albinos, and hopefully, some Retics!
So, try the method I use, and let me know if it works! Some of my males are easier to get "conditioned", and others just don't feel like mating/calling at all lol.