The shear center of an open cross section is the point where the resultant moment of external forces and internal stresses in the plane of the section must be zero.
For most common rolled shapes, the location of the shear center is illustrated in AISC Design Guide No. 9 Torsional Analysis of Structural Steel Members (a free download for AISC members at www.aisc.org/epubs). See Figure 2.1. For symmetric shapes, the shear center is on the line of symmetry. For doubly symmetric shapes, such as W-shapes, the shear center is at the centroid. For channels, see Figure 3.1 and the associated equations for e0. For angles and tees, the shear center is at the intersection of the mid lines of the elements of the cross-section. If you are looking for the general location of the shear center with respect to the geometric axes for other shapes, I suggest looking at the information in Design Guide No. 9 or a structural steel design textbook.
Design of Steel Structures