How do you encourage more babies from a guppy female like more fertile eggs?

You do the same thing for a Guppy as you would do for any fish you wish to breed with. You go way better than the minimum requirements for the amount of water they need, and you feed the fish some livefood at least a couple of times every week. Guppies are of course livebearers so they will never lay eggs. The basic rules for keeping any kind of fish are. 1 inch of fish needs a minimum of 1 gallon of water.(for breeders, at least 3 gallons per inch) :- Every tank needs a permanently running cycled filter. Every tank needs to have at least 50% of it water changed every week. Comply with the above rules and your fish stand a chance of surviving. Fail to comply with them and I can guarantee that your fish will have constant health problems.