Methods are disclosed for preparing a highly active solid metallocene-containing catalyst system and its use in the polymerization of olefins. The catalyst system is prepared by creating a catalyst system solution by combining an aluminoxane with a metallocene having a substituent which has olefinic unsaturation in an aliphatic liquid to form a liquid catalyst system, conducting prepolymerization of an olefin in the liquid catalyst system, preferably in multiple stages, and separating the resulting solid metallocene-containing catalyst system from the reaction mixture. Also polymerization of olefins using the inventive solid catalyst system is disclosed.