The change of the trichromes is what you look for...when they go from cloudy to amber or somewhat of both. I have heard that if you want a more energetic, heady kind of buzz you harvest when the trics are cloudy. For a more narcotic, couch lock type thing you want more amber. If the trics are still clear it's too early.50/50 is what most go for....I have also in the past taken the ripened ones as they ripen...this allows for the bottom buds to swell another week or so instead of chopping the whole thing down