If the majority of the trichs are cloudy with maybe 10%-15% amber, that is when I'd harvest. Harvest a little earlier for more of a head high, or a bit later for a more narcotic (sedating) effect. If you haven't done so yet, be sure to flush with plain water a couple of times preferably a week or two before harvest. This helps to wash away excess ferts from the roots which can give the buds a sharp unpleasant taste.