In the current environment of precision treatments for cancer, what kind of genetic alterations can be categorized as actionable? What other criteria would make a genetic alteration actionable?

In the current environment of precision treatments for cancer, what kind of genetic alterations can be categorized as actionable? For example, if the mutation is linked to an approved therapy in the solid tumor under study or another solid tumor (e.g., ALK rearrangement in lung or breast cancer, respectively)? What other criteria would make a genetic alteration actionable?