It often takes some time for a colony to get going. Usually 2-3 weeks before they get comfortable enough with each other to start "doin' the deed". Temperature also plays a role. They don't like it hot, so fall through early spring are typically the best production times.
If you use plastic to keep your rodents, make sure you get bins that have no edges or impressions on the inside of the container. Mice and rats will chew on anything they can wrap their teeth around, and it doesn't take long to chew a hole in the bottom where the impression for the "feet" of the bin are. If you can't find one with no edges or impressions inside, make sure you get a strong, stiff plastic, not a "rubbermaid" or "sterilite" type of soft plastic.
Ventilation is also very important to production. If you have a glass or plastic enclosure, you need to have 3/4 or more of the top with screen or wire to allow proper ventilation. Without proper ventilation, the mice will either not produce, or they and the offspring could suffer illness and respiratory infections. Avoid pine shavings if you are using an aquarium with screen lid...too much dust.
Quiet. Security is key to production. Mice in a high-traffic area will not feel as secure and comfortable as mice kept in a cool, dark, quiet area, and may lower production numbers. Along with this security comes necessities. Mice that always have access to food and water will produce more readily and higher numbers than mice that are unsure of their feeding schedule.
Other than that...boys and girls together, and let nature run it's course...
