Normaly you harvest when about 70%of the pistils on the buds turn colors and or when the buds stop growing. Some of the leaves will turn color as well.
Yes, read. Quickie answer is: when your trichs are cloudy and starting to turn amber/brown. You could go by pistils, they are a very visible indicator, but best to use a magnifying glass to examine the trichs.
toastybiz is right, but that method is very advanced to see when the trichomes are ready. Basically before growing you need to see what the recommended flowering time is for that breed. They vary alote.