Im not sure if there are any tricks to it but there a few things that i think are important.
- Atleast one male and female that are in prime condition, they seem to mature in a few months if they grow well.
- Enough water for them to spawn in, something about the size of a 2' tank works but it could probably be smaller.
- Rainy weather seems to trigger breeding so either put them outside in the rain or just open windows to let the rainy air in and spray them with rain water.
Also if you want them to breed at this time of year you would probably need heating.