I agree with them about the 1:2-3, but from a breeding stand point if you have the breeding guppies in a 10g and have a seperate tank for the fry you could do 1:4 or 1:5 male to female ratio. The more females you have the more fry you are going to get.
Make sure to either pull the fry or have dense, heavy, floating, midlevel, and bottom plants. In my experience the fry tend to stay near the bottom of the tank after they are a couple of days old, but the first day or two they try to hide as near the surface as they can, but your guppies may be different.
Good luck.
