Well here is the info for knowing when they're ready and during spawning.
If he's ready he'll build a nest. Between building a nest and flaring at the female he is easier to judge when he is ready.
The female shouldn't flare back at him, but she should try to break through the glass to get to the male. If she is dark colored then she should show verticle bars and swim with her head down.
If the male has a head start on the bubble nest you should release the female. Don't leave them unnatended for any amount of time during this period. But keep a distance since they like their privacy, lol.
He will bite and chase and pretty much drive her crazy, but it's betta love :P.
She will go hide from time to time (actually yesterday I had my female jump on to the corner filter and out of the water. lol.). He will go back to nest making and when he's done he'll go and look for her. Once he finds her he'll try to gently get her under the bubble nest. If she likes the nest she will start showin him she's ready. They will start nosing each others sides and then he will flip her upside down and squeeze the eggs out of her. This is known as 'the embrace'. Usually the first few embraces have no eggs but they soon start producing 1-50 eggs per embrace. They will do this for 2-10 hours. When she's out of eggs he figures he's done with her and chases her away (men, geeze we suck :P). Remove the female and place her in a clean jar with one drop of methylene blue.
Now the male has control. He mouths the eggs and pushes them and catches any that fall. About 24 hours after spawning the eggs hatch and the fry's little tails hang down from the nest. About 36 hours of hanging in the nest the fry become free swimming. Remove the male and put him in a clean jar with 1 drop of methylene blue.