Pay attention to your porosity.
As a reminder, your curl porosity is how porous your curls are (i.e., how much water they can absorb and repel, like a sponge). Curls with low porosity require lightweight products—and lightweight cleansing conditioners—to look their best (heavy formulas can quickly build up and weigh down hair), while curls with high porosity need conditioners rich in butters, oils, and proteins to keep them healthy. The quickest way to find out your type is with a porosity quiz, FYI.
Read the ingredients.
Like, actually though. If you're looking for a rich, ultra-moisturizing cleansing conditioner, look for shea butter, coconut oil, castor oil, and olive oil toward the top of the ingredients list. The more hair oils it has (especially near the top), the heavier it'll be. Need a lighter-weight cleansing conditioner? Look for a formula with only a few lightweight oils, like argan and almond oils, and avoid any co-wash that has shea butter or coconut oil in the front-half of its ingredients.
Be mindful of the packaging.
Another thing to consider is what type of packaging your cleansing conditioner comes in. It may seem like a minor detail, but if you don’t like the way that the formula is dispensed, you’re not going to want to use it. Believe it or not, packaging was one of the biggest gripes among reviewers for these co-washes. There are jars, pumps, foams, and more, so think about what might be easiest for you. The consensus among most reviewers is that pumps help dispense cleansing conditioners best.