You should veg (18 hrs a day of light) for 4-6 weeks before you cut back to 12hrs of light a day for flowering. Once you cut back you should see flowers 2-3 weeks later. Do not interrupt the dark cycle once you go to 12/12. This will cause hermaphrodites.
yeah, it's really up to you when you flower them, your height restrictions are the biggest thing, although you do have to wait longer if they are from seed rather than clones.
