In this work I used a code of galaxy formation (GALICS) to explore three different points that are relevant to the the problem of galaxy formation. The first deals with the method of simulation itself, the second considers the simulation of infrared galaxies within GALICS and the third investigated the role of galaxy formation in measurements of weak gravitational lensing.<br /><br />I examined the predictability of models such as GALICS, using an exploratory test, based on the response of the model to variations in the parameters controlling star formation. I have also proposed a new description, in the astrophysical context, of merger trees.<br /><br />I helped to implement new physical prescriptions into GALICS to bring the model into better agreement with the available observations of infrared galaxies. <br /><br />I wrote a code (LEMOMAF) to simulate the weak lensing effect, taking advantage of the coevolution of galaxies and dark matter included in GALICS.