The most helpful way that I was taught to identify the configuration of stereocenters is a right-hand/left-hand rule. First, assign priority numbers to each of the substituents according to atomic mass, or the atomic mass of their first point of differentiation. Next, identify the direction that the substituent with the lowest priority is pointing in (into the plane/paper, out of the plane/paper, or parallel with the plane/paper). Then imagine that your thumb is the lowest priority substituent. If the fingers of your right hand can curl in the direction of the 1-2-3 substituents, then the configuration is R. If the fingers of your left hand curl in the direction of the 1-2-3 substituents, then the configuration is S.
I found this method to be extremely helpful because no matter the orientation of the stereocenter, this method will work because you can adjust your hands to match the orientation of the stereocenter and identify it as R or S.