12/12 is the process in which you flower the plants. When growing out female plants you only want to smoke the flower part of the female plant.

Most people will veg their plants for about 30 day's give or take. It depends on your experience and your style of growing. Veg is a min of 18 lights on and 6 lights off.

Once you decide to put them into flower after the first week of a light cycle of 12/12 you can start feeding them some nutrients for the flower cycle. I.E. Bloom nutrients are now added at this point to enhance your veg nutrients.

It takes about 50-60 day's or more for the plant to finish budding but it's imposable to guarantee that here. Factors like nutrient quality, light, ventilation, temperature it was grown under, stress, and even the strain can all affect how long it take to flower.

You will only know when the proper time to harvest is when all the Trichomes are cloudy and only about 10-20% are amber. You can only view them with a 10x or more pocket microscope. A 30X lighted pocket microscope is the best.

There is a lot more to know like Ph control and knowing your strain but that is the short quick version.

You may want to read up on more specific information before you just post general questions that are to hard to get a straight answer.

Happy growing.