Here is some good/practical info I found at the above website about harvesting:
"Because most hops are produced out of reach from the ground, it is safest to lower the vines in order to pick the hops. The harvest date varies with variety and location but will become evident as you gain experience as a hop grower. At maturity, the hop aroma is at its strongest and is measured by crushing a cone and smelling it. The yellow lupulin glands in the cone become much more evident and plump looking when magnified.
The cone will develop a drier, papery feel and in some varieties a lighter color as it matures. Some browning of the lower bracts is a good sign of ripeness. Squeeze the cones as they develop and you will notice they become more light and resilient rather than green and hard. The actual picking is self-explanatory and this is where you want the flower cones, not the leaves. I don't know why raw hop cones are occasionally called leaf hops, when the idea is to not pick the leaves."
And, here is some helpful info about drying:
"Drying can be done in a good dehydrator, custom made hop dryer, well vented oven, or they can be air dried. If you use heat, the temperature should not exceed 140 degrees F. Cooler temperatures take longer but a higher quality hop is obtained. Under dry weather conditions, I suggest taking a screen off of your house and setting it up in a wind protected area, elevated on each end. Spread the hops as shallow as possible and fluff daily so moist inner cones are brought to the outside of the pile. If weather is dry and the pile is not too thick they will dry in about three days.
A high moisture content in the cones will adversely affect storability and recipe formulation. The hops are dry when the inner stem of the cone (strig) is brittle and breaks rather than bends. The strig takes much longer to dry than the bracts, so be patient. Pack the hops in an air tight container and store in a freezer until used."
I appreciate what is said about using scales on page one of this thread, but I think knowing when to pick--and how to dry--our hops (like the hop farmer writing above) is somewhat of an art that comes with experience, not unlike brewing itself!