Wavy hair does not fit into any mold. It is not curly enough to do anything with nor is it straight enough to go that route. It seems wavy hair has a mind of its own and you can do little to manage it. While it is true that wavy hair is a challenge, there are things you can do to tame it and make it easier to handle.
Wavy hair tends to be dry. When a person has dry hair it is recommended that you only wash your hair every other day or every third day. Washing it more often than that strips the oil out of it and adds to the dryness problem. Also, people with wavy hair need to use a moisturizing shampoo and conditioner. If battling extreme dryness near the ends, they can put olive oil on the ends of their hair for 10 minutes and then rinse out.
If your dry wavy hair also has a dry scalp that tends toward dandruff, try to add a half a teaspoon of baking soda to your shampoo to remove the dandruff in the hair. This also works if you have dry hair everywhere except on the scalp, where it is oily. The baking soda just removes all of the bad stuff. This is a better alternative than using a clarifying shampoo which will dry your hair out and strip it of everything.
Keratin shampoo is good to use on wavy hair but it is best to not use it every time. It works better when used once a week or once every two weeks. It helps to make hair more manageable.
If you have wavy hair and want to straighten it, be sure to do it safely. Use a thermal protectant and hair oil to help achieve the smooth look you are craving.