When and where to go spot celebrities attending the Paris fashion week !

Im here for a month so i would like to kinda see celebs/models from the sidelines. If a show starts at 8pm, what time should i go to spot celebs attending the show? 

Also where exactly can i find them, perhaps outside the louvre but i bet it will be quite crowded, is there any other spots where i can see them coming in/out of these events?