Check your trichome heads with something. A camera, jeweler's loupe, magnifying glass, it doesn't matter.
While you're checking them, you want them all to be at Least cloudy, not clear. Cloudy and amber heads are what you're looking for.
Don't harvest until all of them are at least cloudy.
If you like couch lock buds, let it grow until about 40%-50% of the trichome heads are amber, then harvest.
Happy harvesting!