I sorted my strips into piles; whites, browns and greys. I have a frame with a large working area that gives me lots of room to layout my strips close to my work. This is very helpful in quickly picking out the right value.
Hook in short strokes, no longer than the actual length of hair that your particular animal has. For instance, when hooking a Boxer your strokes should be shorter than if you were to hook a Sheepdog.
Always hook in the direction that the fur grows.