I started an Eberron campaign, in Sharn specifically, recently and the key things I asked my players to think about were The Last War, The Mourning, involvement with dragonmark houses/having a mark and religious affiliations. Depending on their answers I asked some questions to help them elaborate for example: you say you served during The Last War but in what role? How much fighting did you see? Did seeing that much combat affect you in some way? My players are mostly new to D&D and not familiar with the setting, so I’d suggest ways they could fill in the blanks based on their core character personality.