This chapter is dedicated to methods of aerodynamic characteristic determination that have specifics for tandem wings. Firstly, a comprehensive analytical method is presented. Its main advantage over previous theoretical approaches is the possibility to evaluate roll moment, as well as moderate dihedral angles and sweep angles of the wings. Also, it takes into account the contraction of tip vortices to the symmetry plane that improves the accuracy of downwash/upwash prediction and, therefore, lift and drag. The second edition of the book includes a method of damping moment determination specific for tandem wings. Then used CFD methods are presented: 2D, low-level and high-level 3D (up to Reynolds Averaged Navier-Stokes equations) depending on the development stage and accuracy required. Found limitations of the numerical approach for a tandem wing case are discussed. Next, there is a description of a wind tunnel model of a UAV with which multiple tests (weight and visual) were performed. Finally, the comparison of predictions by all the methods is presented including control surface effectiveness with wing-wing interference.