Hi,
Well, the first thing is to make sure that you have a healthy, viable, preferably unrelated pair. Age/size of the male is not as important, but you need to make sure that the female is fat, large and preferably at least 2 years of age. They can mate at younger ages, but it can cause serious health issues and she will have a much higher chance of egg binding.
Some frillies need a "down time" prior to breeding. This brumation period can be achieved by lowering temps and keeping the humidity at a lower level. This is not all together necessary for breeding, but it does seem to help. This dry period is then followed by a boost in temps and a lot of spraying. About a month-3 months after this change, you tend to see breeding behavior. Males will frill and bob their heads. Females that are receptive will spend a lot of time on the ground (they breed on the ground).
Once a female is gravid, you need to make sure that she has a lay area to deposit her eggs. If she doesnt, she can egg bind and die. Lay areas should consist of moist, but not wet substrate such as soil, or a mix of soil and sand. Females typically go down, dig and lay in one shot unlike many other lizards that dig multiple lay areas.
Unearth the eggs, put in a dish with moist, not wet vermiculite and place in an incubator 80-85 degrees. It takes 60-90 days for the eggs to hatch.
Hope that helps.
Dana