Frizz can be caused by a number of things; most commonly is a lack of moisture. Weather, products, build-up, hard water and techniques all play into it. This link was really helpful to me when I was first learning what my hair needed:
Live Curly Live Free - Curly Hair Basics
3B, fine, normal to low porosity
Modified CG since June 2010
HGs: FSG, anything with glycerin, Tresemme Naturals conditioner, Curls Like Us cloths, satin pillowcases.