Heat the solution to concentrate it, then leave it in a warm place, then partially evaporate the solution and allow to cool filter off crystals. Pick out the crystals, then dry the crystals with filter paper.
I take issue with the answer by Randomized. That process will prepare CaCl2.2H2O or some other hydrated form of CaCl2.xH2O but not anhydrous CaCl2. In fact, anhydrous CaCl2 can only be obtained in a fleeting time period. DRY and anhydrous CaCl2 can be prepared by heating the solid obtained by Randomized process to drive off the water of crystallization. The dry product is called fused CaCl2. It is so hygroscopic (in fact it is deliquescent) and immediately starts absorbing moisture from its surroundings. It is used as a drying agent for that very reason. I have been told that the only way to keep it as anhydrous CaCl2 is to transfer the fused CaCl2 to a heated dry box.
