The concept and use of local orbitals are deeply connected to the history of Quantum Chemistry. Indeed, most types of bonds are explained through the concept of bonding and antibonding local orbitals. We describe here the main procedures that can be used to obtain localized orbitals. After a brief description of the underlying formalism, the different algorithms are compared through the application to simple systems. It is possible, in this way, to emphasize the advantages and inconveniences of the different approaches.