Incroquat BTMS) or cetrimonium bromide, or some variation thereon.
You remember how surfactants work, right? (If not, please click here.) Surfactants are wetting agents that lower the surface tension of liquids and lower the interfacial tension between liquids - in other words, they emulsify. In a shampoo, we use anionic surfactants to create a lathery, bubbly creation. In lotions, we use non-ionic surfactants to create an emulsion. In conditioners, we use cationic surfactants to condition. These cationic surfactants also create emulsifications - ever use BTMS as an emulsifier? - which will remove the dirt and soil from your hair.
In the shampoo post from earlier today, I mentioned the three ways shampoo cleans your hair - the roll up, the micellular solubilization, and the dispersion and emulsification mechanisms. The latter two mechanisms are the key to the no 'poo method. The roll up mechanism does not work with the cationic quaternary compounds: Because there's no detergent, there's no displacement of oils by said detergent. The cationic compounds are good emulsifiers, so they will help solubilize and emulsify the oils and soils on your hair so you can rinse them away.
There is also a theory that electrostatic repulsion between the soils and the hair fibres are enhanced by anionic surfactants, which are dissolved into the shampoo. If you're using cationic ingredients, you won't see that repulsion and the soil can remain on your hair and scalp.
Does this method work? Thousands swear by it and love it - anecdotes do not data make, but it does have some promise for dry to very dry hair and for those who experience a lot of breakage. If you're an oily haired girl, this method is probably not for you as it is not great at removing sebum. If you're someone who uses a lot of hair styling products, if you want to try this method you'll want to choose something with cetrimonium chloride because it is awesome at removing silicones!
I've tried this method and it doesn't work for me. I have oily hair. After washing only with conditioner, I could still feel the oil on my scalp and hair, and I felt seriously unwashed.
I can't really make any suggestions for conditioners you might want to use but you will need to use something with a cationic ingredient (see above) and you will want something with cetrimonium chloride if you're using styling products. I thought it would be fun to see the difference between something called a cleansing conditioner and a regular old conditioner off the shelf. Kim sent me the ingredients for the Wen conditioner, and I chose the Neutrogena product because it contained behentrimonium methylsulfate (found in BTMS).
Let's take a look at the Wen Mint Sweet Almond Cleansing Conditioner ($28 at Amazon.com)
Water, Aloe Vera Gel, Glycerin, Chamomile Extract, Cherry Bark Extract, Calendula Extract, Rosemary Extract, Behentrimonium Chloride, Stearamidopropyl Dimethylamine, Cetyl Alcohol, Emulsifying Wax, Panthenol, Trimethylsilylamodimethicone, Hydrolyzed Whole Wheat Protein, PEG-60, Almond Glycerides, Menthol, Essential Oils, Citric Acid, Methylchoroisothiazolinone, Methylisothiazolinone, Fragrance
The ingredients we care about are the behentrimonium chloride, stearamidopropyl dimethylamine, and trimethylsilyamodimethicone (a silicone), which are all conditioning agents. The cetyl alcohol will boost the substantivity of the conditioners, the panthenol is great for damaged hair, and you know I'm a huge fan of hydrolyzed proteins as film formers. The almond glycerides may help moisturize your hair. In short, this looks like a fairly nice conditioner. (Although why there's e-wax in there, I have no idea! Probably for the "cleansing" part?) We also know rosemary extract can be good for oily hair, so this will remove some of the sebum.
Neutrogena Triple Moisturizer Daily Deep Conditioner ($6.19 at drugstore.com) has these ingredients...
Water, Cyclopentasiloxane, Behenyl Alcohol, Behentrimonium Chloride, Cetearyl Alcohol, Cetearyl Alcohol, Cyclohexasiloxane, Dimethicone, Amodimethicone, Behentrimonium Methylsulfate, Stearamidopropyl Dimethylamine, Cetrimonium Chloride, Panthenol, Sweet Almond Oil (prunus amygdalis dulcis), Olive Fruit Oil (olea europaea), Meadowfoam Seed Oil (limnanthes alba), Glycol Stearate, Ceteth 2, Hydroxyethylcellulose, Methylparaben, Propylparaben, Citric Acid, Titanium Dioxide, Iron Oxide, Mica, Fragrance (Parfum)
I don't buy conditioners - I make my own - but this looks to be a nice one filled with all kinds of cationic conditioning agents and boosters, silicones, and a little cetrimonium chloride thrown in for good measure. If this looks too intense for your hair, the Neutrogena Clean Conditioner ($4.99 at drugstore.com) is very similar with no oils and fewer silicones.
What's the big difference between these two? Cost, I'd say. The Neutrogena product has far more conditioning agents and things actually good for your hair (oils, silicones, fatty alcohols, and cetrimonium chloride) and costs a whole lot less. It'd be great for someone who uses a lot of styling products on her hair - the cetrimonium chloride can remove it. There isn't anything inherently more cleansing in the Wen conditioner than the Neutrogena conditioners, but you'll save a ton of money by going to the drug store armed with your knowledge of what ingredients matter!