To learn how to select gem rough well you have to have experience in cutting that material. We can advise you to select only eye clean material free of cleavages of well colored material, but until you have experience cutting the stuff you won't understand about how the stones need to be oriented to produce the best color and yield for each individual piece of rough. You need to also understand something about the optical characteristics of the stone, what its cleavage is, its great differential hardness and where in the stone to place minor flaws so that they will be less obvious in the finished stone. Perhaps find a cutter that knows how to cut kyanite and then let him sort the rough and pick out the material with the best potential.