This paper presents a generalization of many particular results about special types of filters (e.g., (positive) implicative, fantastic) on algebras of nonclassical (mostly fuzzy) logics. Our approach is rooted in the framework of Abstract Algebraic Logic, and is based on the close connection between the filter-defining conditions and alternative axiomatizations of the logics involved. We identify four main kinds of theorems proved in the literature and we formulate general theorems which (provided a simple syntactical proof) yield the majority of published results as their direct consequences.