Bad tangles can be the result of a few different things (or any combination):
Needing a trim- split ends cause more tangles and yanking at tangles causes more split ends. It's a vicious cycle
Using a product your hair doesn't like- have you determined your hair properties (texture, porosity, etc)? These can make a huge difference in the products that will and won't work for your hair. Then there are some ingredients that some people just find to be a problem for their hair for no real reason: polyquats, glycerin, magnesium sulfate, to name a few. Try to note if your hair tangles more or less with certain products and compare ingredients.
Plain old friction- are you pineappling or using a satin sleep cap or pillowcase at night?
I'm not sure if you're following CG or not, but one thing I've observed with my own hair is that I can use silicones in my styling products without any issues, but when my cleansers or conditioners contain silicones my hair feels much drier and is definitely more prone to tangles (I'm modified CG, so I do still use silicones and sulfates on occasion).

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Modified CG since 11/5/11
CLEANSE: CJ Daily Fix, DevaCare No-Poo, CHS Treatment Shampoo
RO: SS Caitlin's Conditioner, CJ Beauticurls Strengthening
LI: SS Repairing Protein Treatment, CHS Silk Leave-In
STYLE: Re:Coil, Curl Keeper, Deva Ultra Defining Gel, Curls Rock Amplifier,Sweet Curls Elixirs Okra Gel and Hard Hold Gel, SS Curl Enhancing Jelly and Firm Hold Gel