eh, it's hard.
I mean, the only thing you can really test is the high. the taste takes curing to really show, and that takes atleast a month and a half.
I'd take something inbetween a huge bud and a underling . . . one of those middle-ground buds that are just as good as the big ones.
but basically, you're gonna want to be looking at the trichomes to decide the best time to test. when the trichomes are totally white(cloudy) that's an ok time, a lot of people like to let the trichomes go 50/50 amber/cloudy . . . up to you. plenty of info on the forums about that.