The male betta will build a bubblenest-- he's always ready to spawn!

When the female is ready for spawning, she will have pale vertical lines showing across her body (only dark colored bettas will show this).

Put them together and they will chase each other around for a bit. Make sure the tank has places for the female to hide if she's not quite ready. Shredded fins on both parties are likely at this stage, though particularly on the female.

Eventually the male will embrace the female, wrapping his body around her.

After the embrace, the female will often float at the top of the water, looking dead – don't worry! – she's just resting.

The male will be swimming energetically around looking for eggs. (Not every embrace will have eggs.)

After gathering the eggs in his mouth, the male will swim up to his nest and put them into the bubbles.

Then the bettas will embrace again and the sequence starts again. They will often continue this for hours.

(I usually remove the female after there has been at least an hour with no embracing, and if the male is actively trying to drive the female away.)

The male guards his nest vigilantly, often moving the eggs around to "better locations" and building up the bubblenest around them. (Some bettas will never have much of a nest – others will build a nest that sticks out of the tank!)

Happy fish! Now everybody is just waiting for the eggs to hatch!