The fundamental frequency of a plate can be raised by placing appropriate number of rigid supports at various optimal locations along the nodal lines of vibration modes, as previously shown by other researchers. Unlike previous works, however, the present study aims to determine the optimal locations and the corresponding minimum stiffness of elastic spring supports using a direct search optimization method, presuming that the nodal lines of vibration modes can be identified a priori. As examples of applications, the optimal locations and stiffness are determined for isotropic plates and laminated composite plates with various lamination schemes, results of the latter are presented for the first time in open literature. Although only plates with regular geometry are treated in this preliminary study, further extension to plates with irregular geometry and other boundary conditions is being carried out.