Well firstly , when to harvest is a matter of preferences with a few guide lines . You don't wanna be harvesting when your plant still has mostly clear trichomes , this will give you poor quality "stone". You typically wanna wait until most of the trichomes are milky/cloudy accompanied by some amber ones my prefered ratio is 80 milky 20 amber . Moving on to some of the signs that your plant is ready for harvest . Your plant will give you signs when its nearing the end of its life cycle you will notice that your plant will stop pumping out calyx hairs , she will slow in the swelling of the flowers , leaves will turn yellow or different colours for seemingly nothing . These are a few of the signs you can look for to ensure that your going to get maximum yield and potency as well . Another simple way to ensure your plants are done before you harvest them is to check your seed banks recommended flowering time and add 2 weeks to that time . I say this because often times plants wont be ready in the ammount of time they say , yes you could cut them down on the day they suggest and still get good bud , but to get even better product from it I usually give it 1 - 2 weeks longer . Another reason I say this is because most of us can't replicate the exact exact enviroment that the breeder made their seeds so that leads to extra time often in grows. Lastly , you can get tools that will help you look at your trichomes on your plant to better help you determine when you wanna harvest exactly , these tools are common and can be found in a variety of places such as Amazon , Wal mart , Camera shops , Grow shops , Ebay , the tools are a "Portable Microscope" and "micro lense" both of these tools are inexpensive and will greatly help in the department of determaning when your plants are ready by allowing you to see the plants trichomes up close and personal so you can see if they are clear , milky/cloudy or amber . Other then that there isnt really much else to discuss on this topic I hope the information provided helps you on your journey to becoming a Grow Master !! -Happy Growing!