as much wood as a woodchuck could cuck if a woodchuck could chuck wood.
pretty wide window for personal preference...and whatever flavor genetics add to that equation...
get a 30x loupe - cheap, expensive doesn't matter too much. i'd suggest one with a glass lense vs plastic at the least.
trichomes - 10-100% amber dependin on who you talk to.. you'll have to try it out yourself and figure it out.
pistils -- at least 50% but oftent imes they are 100% colored by the time you see amber trichomes.
density - i'd hold off on this when you've pretty much made up your mind and you gently touch a few colas high/mid/low to see how dense they are.
using a few indicators will keep you consistent.. when they visbily look like buds, figure 14 more days give or take and that's an early window.