In a recent highly collaborative publication in Phys. Rev. B with colleagues from Sweden, Italy, Russia, France, and Spain, we report on a systematic investigation of the transition metal-doped topological insulator Sb2Te3. By combining density functional theory with complementary experimental techniques, i.e., STM, resonant photoemission, and x-ray magnetic circular dichroism, we achieved a detailed characterization of the electronic and magnetic properties. Our results provide general guidelines how to realize a robust QAHE by doping Sb2Te3 towards a ferromagnetic state.