This paper deals with relative normalizations of skew ruled surfaces in the Euclidean space \(\mathbb {E}^{3}\). Firstly we investigate some new formulae concerning the Pick invariant, the relative curvature, the relative mean curvature and the curvature of the relative metric of a relatively normalized ruled surface \(\varPhi \) and we introduce some special normalizations of such surfaces. Then we determine all ruled surfaces and their corresponding normalizations that make \(\varPhi \) an improper or a proper relative sphere. Finally, we study ruled surfaces, which are centrally normalized, i.e., their relative normals at each point lie on the corresponding central plane. Especially we study various properties of the Tchebychev vector field and of the relative image of \(\varPhi \).