From the looks of it that is a indica dominate strain judging by the wider leaves and close internodal spacing... a good way to determine when to harvest is the hairs... when 1/3 of the hairs dry out and turn redd/orange the high will be a more clear cerebral high with alittle body high depending on the strain. The longer you let it mature the more lethargic the high will be... Its best to get it around 50% of the hairs dried to get a good mix of mental/physical high. If you are up to it the best way to determine when to harvest is to get a good strong magnifing glass and look at the little mushroom-shaped resin glands... At first they will be clear.. then turn white and cloudy and as it matures itll turn amber.. The key is to try to harvest when most of the glands are white... If you want a more couchlock high then wait until a few glands have turned amber, if you want a clearer less debilitating high then get it when alot of the glands are still clear and few glands are amber. The very tip of your main cola will ripen the soonest so check the lower buds too before determining the ripeness of the buds.