Being a curly girl can be tricky because conventional hair care that we are all familiar with doesn't
necessarily work for us. I don't like that "normal" haircare is geared towards straight hair, because there are so many hair textures and even curly haircare doesn't have just one method. We have different curl patters, different thicknesses, different degrees of porosity, and react differently to products. For example, my hair can be weighed down easily so even if my hair needs moisture, I have to be careful with oils and creams. Even though protein is good for hair, some people's hair don't react well to it and can cause buildup.
So what's co-washing? It's when you skip using shampoo and "wash" your hair using conditioner instead. Now co-washing can be done by anyone, but especially great for curly haired girls since we need the extra moisture. The problem with shampoos is that along with dirt, it also strips away all of your natural oils. The main thing to look out for in shampoos are sulfates. This daily stripping of your natural oils dries your hair out and adds on to the frizz. Another thing to keep in mind is that curly hair is more porous, so when you shampoo it can get stuck in the shafts and not get fully rinsed out. Using conditioners to wash your hair is surprisingly sufficient, though. Conditioners usually have surfactants that will help to clean your hair, but it may take some getting used to.
Taking it a step further, you may want to opt to wash it every few days (even once a week depending on your hair type) because among other reason, even the water you are washing your hair with can damage your hair (I know, I know, I'm not trying to sound like one of those people that say everything is dangerous for you). It's true through, I remember hearing on the TV here that the water in the US has so many chemicals in it that hair care products like shampoo and conditioners are a lot "stronger" than products in Japan.
To help ease into the co-washing world, it may help to use products that won't cause a lot of buildup. For example, silicones will need to be washed out with shampoos, so those gotta go. Styling products like waxes will also cause buildup. Also, "clarifying" your hair with no poo products or even all natural methods like vinegar and baking soda) will help out.
Pick a good conditioner for this, though. If you're one of those people whose hair doesn't react well to too much protein or other ingredients, make sure that you look into the ingredients first. Do a bit of research about ingredients to learn about humectants, emollients, and proteins, which are very important for curly hair.
Just because you have curly hair doesn't mean that you need a ton of products. If you know your hair type, and know what works for it, it makes it a lot easier to manage. Take out the things that cause frizz and damage, and add moisture and things that will help hydrate and create healthy, defined curls.