From playing and running many years of MET VtM I've seen some outlandish characters and backgrounds (3rd in Line to the English Throne?!) so here's some advice I'd recommend.
Speak to the Storyteller
Especially for games that are already running there are trip-ups when you start play, but this can happen for new games as well as the land-grab of resources and backgrounds, feeding grounds, places to live, etc etc start.
Before decided anything about your character that isn't trivially mundane consider how it might affect the story. Are you claiming ownership/control of a local resource? Someone else in play might already control it - ooops!
Are you creating a famous nightclub in an established game? Why might no-one have heard of it before? These things don't pop out of nowhere.
Good advice if you want something for your character (Such as a Theatre) as what's available in the city/region/etc for your character to control, this gives you real game resources to link into and use.
In larger (worldwide) games people can make outlandish claims that they don't consider other things going on - we had one player in Boston USA whose character was apparently prince of Cambridge (UK) for ten years - without ever asking or checking with the people who were running a game there!
Speak to the other players
Politics is the primary force in most VtM games, connections and links are key, you can get a lot by asking other players for link ins or background crossovers.
Maybe you worked with another vampire a while ago on something that they've already got
Maybe you are the prodigy of an existing character (a great tie in)
In VtM this will primarily be members of your own clan, speak to the Storyteller and they may be able to get you some people to talk to; often games like these have mailing lists and even newsletters for clans and/or domains to keep the atmosphere rolling.
Never use anyone famous
This happens again and again in backgrounds and it's just annoying to Storytellers; unless you have permission don't name check anyone that is famous in the REAL world, they may not even EXIST in the VtM world or may even be dead/a werewolf, who knows! If you want a link, again, speak to the storyteller.
@ladenedge has some excellent advice for generating character background, so I'm not going to cover that.