A saturated solution of a substance in water can be prepared as follows:
Take about 100 ml of water in a beaker. Keep this water at the desired temperature by using a water bath. Add a small quantity of the given substance into the water and dissolve it by stirring. Add a little more substance and again stir to dissolve it. Continue dissolving more and more substance until a little substance is left undisclosed at the bottom of the beaker. Keep the solution so prepared at the desired temperature for a few minutes. The supernatant solution is saturated solution of the given substance in water at that temperature.