Bucky, that advice is somewhat unsound; if you are not well versed in betta breeding, please do not offer advice.[/offtopic]
First off - have you researched breeding thoroughly, read the site's
FAQ, obtained a healthy breeding pair from a breeder (not just store bought VTs), purchased the needed jars and grow-out tank, prepared the spawning tank, conditioned both fish, studied the geneology for projected results, etc.? I'm guessing not, since you are uncertain of how to tell if the female is ready, so please do all of these things before embarking on breeding; it will only benefit the pair and the fry.
Anyways, when a female is ready to breed, she will exhibit vertical breeding bars. It will look almost like stress stripes, but vertical instead of horizontal. She will also become extremely round-bellied and laden with eggs.
Also, please do not just "try it out" as suggested. You need to condition both bettas properly for breeding (I think we have an FAQ on this on the board), and place the female in an enclosed container in the spawning tank for the male to view for @ least 24 hours. During this time, they will become used to one another's presence, and the male will build a bubblenest. The female usually becomes more egg-laden in this time and will exhibit stronger stripes.
If you place them together before a bubblenest is made, and when they are completely unused to one another, you will only have fighting, with possibly fatal consequences. If you do not condition, you may have little or no fry, or weak fry.
