trichomes (30-60x magnification to see them properly) --
pistils --
density --
No 1 is perfect. They all have flaws for choosing harvest date, some more than others.
One thing i'd point out is that shaving off a day or two after 3-4 months doesn't actually save you any time, so be patient. Let that bud ripen up more. those hairs are very long. Sometimes plants have white and/or long-ish hairs remaining even though it is ready for harvest. Like i said all three have limitations and exceptions. Sometimes trichomes just don't turn amber at all. 10% 50%? 70%? i dont' know what's best.. and that comes down to your opinion within a common-sense window. If you like being droopy dog when high, let it amber up a lot. Some people may feel differently while taking the same drug, so keep that in mind too.. experiement and find what you like. ---
once you do it a few times, it's much easier. Things become familiar and easier to assess.