Use a clarifying shampoo at least once a month. Wavy hair tends to get build-up faster than curly hair. Build-up can weigh down your roots, cause frizz and other problems.
Wear your hair in a loose bun (this is called a "pineapple" in the CGM world) at night to preserve your waves overnight
Try diffusing your hair instead of air drying. For many with wavy hair, diffusing makes waves tighter and gives more volume
Test out wet styling and damp styling to see which results you prefer.
Damp styled VS Wet Styled
When problem solving, try to change techniques first. Techniques make a bigger difference than products.
"Scrunch" your hair while in the shower. This will help your waves spring up and will help hydrate your hair.
Try a sulfate-free shampoo instead of a cowash. For most people with wavy hair, cowashing is too heavy and will flatten roots.