Your plants are ready when all of the trichomes are at least cloudy, some will mature at different rates keep in mind.
If you have a majority of trichomes that are clear, do not harvest.
If you have Majority cloudy with some amber trichomes, that's when I would harvest.
The more amber trichomes you let develop the more body high you will receive
The more cloudy trichomes, the more of a head high you will receive
The best part is you get to decide what you like more (: