As I mentioned in the private message I don't have personal experience breeding betta fish.
I do know from reading info in books or online that they need to be conditioned for a while prior to attempted mating (which is usually done in separate tanks but near each other so they can see each other) increased water temperature, feeding frozen blood worms or live foods, and keeping water super clean (which may mean daily water changes) are all things that have been recommended.
I think a lot of it will be trial and error. You're going to have to try different things and see what works for your fish and situation. The main thing I would mention is that breeding bettas can be dangerous to your fish. Keep a close eye on them and know when to separate them before they end up injured badly or worse.
And don't forget to have lots and lots of jars on hand if this works out for you