i always check the buds for 50/50 clear/cloudy.
I check several places on the plant - and go with an overall average of 30% amber.
Even the breeders can't agree on what percentage (clear/cloudy/amber), and it's a matter of personal preference, but Amsterdam coffee shops often turn away bud that was harvested too early.
Once you think it's finished wait another week. that way you're not going to make the mistake many growers make... because they're impatient, or worried about the smell, or whatever...