you need a mini microscope and look at the tricomes you can harvest anytime from when the trics. are cloudy with a few clear or when 20 % are amber depending on what type of high your looking for,the more amber the more of a couchlock effect,also outdoor plants tend to show amber trics early,you will spot a few that are very amber,I like to harvest when there cloudy and very few amber you can get a scope at radio shack they take a little getting used to but work good luck