Does it work? um...sometimes. OK, does it work for everyone? not really. There are a lot of factors that influence the choice to not shampoo including your own personality. Take me for instance, I'm a little bit of a control freak, so I want to know what my hair will look like most of the time and for me, that means a shampoo, condition, and a styler and or leave-in. I found that when I followed a no-shampoo routine, my hair looked about the same as with a shampoo, if not a little frizzier (probably due to over-conditioning). I also found that psychologically I like to shampoo and it's easier to keep my hair clean. You can get similar results with no using shampoo, but you have to be careful what types of conditioner and styling products you use.
Not into shampooing? Ok, look for lightweight conditioners (like Curl Theory Daily Hair Conditioner) that don't contain too much oil or waxes and ideally, contain surfactants or mild cleansing agents (which also can help with the emulsifying process in the conditioner). Ingredients like Behentrimonium Methosulfate, Behentrimonium Chloride, and Cocamidopropyl Betaine are some good ones to look for in your conditioner for your "conditioner washes". Also, it is very very important that you massage your scalp with as much pressure as you would with your shampoo. This is what helps to loosen and remove dirt and oil on the scalp along with the conditioner. If you are not using the right technique and/or product, you could end up with buildup which can be...not so nice.
OK, you want to use shampoo? Look for a very gentle, clear shampoo, preferably without sulfates (which tend to be harsher) like Curl Assurance Gentle Cleansing Shampoo. Also, try not to shampoo every day and follow with a moisturizing conditioner.