Thick discs are interesting galactic components that are present in many spiral galaxies, including the Milky Way. Observations have revealed that, in general, thick discs are composed by old stars, which leads to the idea that they preserve key information on how their host galaxies came into place and evolved. Thus, by understanding the formation of thick discs we could improve enormously our general knowledge of galaxy formation, particularly in the case of the Milky Way. However, the dominant mechanism leading to the formation of thick discs remains unclear to this day.
In this talk I will present the main results of a study on the formation process of thick discs in galaxies, carried out using numerical simulations. Specifically, I explore the formation scenario in which thick discs are the final product of a merger between a pre-existing disc and a satellite galaxy. In this study I characterise in detail this process and make specific predictions that can be compared to both current and future observations of thick discs, especially of the Milky Way, such as RAVE, SEGUE, Gaia and LAMOST/LEGUE. Special attention has been paid to study the final distribution of satellite debris which could in principle allow us to distinguish this particular model from others.