We review extrapolation methods for calculation of critical points and indices from the perturbative expansions by means of Pad\'{e}-based techniques and their various post-Pad\'{e} extensions by means of root and factor approximants. Factor approximants are applied to finding critical points. Roots are employed within the context of finding critical index. Additive self-similar approximants are discussed and $DLog$ additive recursive approximants are introduced as their generalization. They are applied to the problem of interpolation.