Easy, look for bottles of "flat" enamel or acrylic as opposed to glossy. Being a somewhat experienced modeler, I can give you some more tips:
Always thin your paint before painting. It goes on smoother and lasts longer that way. Enamel paints thin with mineral spirits, acrylics thin with plain old water.
Paint in a well-ventilated area and wear a respirator, even if you're using acrylics, which at first may not seem to give off any fumes. They do, just not as bad as enamels. Build yourself a painting booth if in doubt.
Are you using regular brushes or an airbrush? Airbrushes, while more expensive and requiring more care, generally deliver a superior finish. Of course, regualr brushes are much less expensive, but they wear out and require more effort to get good results. Also, you can't get nice subtle layering effects like you can with an airbrush.