How many days into flowering (12/12) are they? I'm getting close to harvesting my first grow as well and have been asking the same questions and doing as much of my own research as I can. I found this really good article from Hightimes and I think it's the most informative (easy-read) article I've found yet.
http://www.hightimes.com/read/key-points-harvest-time
I hope it helps. Good luck with your harvest!!! Let us know how it turns out. Cheers!
To be honest I have not been keeping time tabs as much for this plant like I did with my 1st grow which was a disaster I though with this current grow I'd let the plant tell me when it's ready.
Thanks for that link it was a good informative easy read and doesn't expand too much on things.
This best advice I can give you is trichome examination daily with a jewelers loupe and generally looking at the condition of the plant. Does she look like she's finishing? Yellowing fan leaves, stopped drinking small subtle things like that.
I hope your grow goes well.