I have two questions. The first one is regarding how to dilute shampoo. I've heard that you should dilute your shampoo with water to make it less harmful to your hair, but does anyone know how much water should be used to dilute the shampoo?

Another question, I've heard some long-haired people on other sites use shampoo only on their scalp and conditioner only on their length. I follow the part about the conditioner, but I use shampoo to wash all of my hair. Is this wrong?

But would conditioner be sufficient enough to clean the hair?

You can dilute shampoo by either adding a bit of water to your hand after pouring the shampoo in, or applying the shampoo to your hair and then quickly ducking under the shower spray.  I use both methods meself :)