Backgrounds describe advantages of birth (or rebirth), circumstance and opportunity: material possessions, social networks and the like. Backgrounds are external, not internal, Traits, and you should always rationalize how you came to possess them, as well as what they
You should think.. Who are your contacts? Why do your allies support you? Where did you meet your retainers? How exactly do you make enough money to justify your four dots in Resources? If you've put enough detail into your character concept, selecting appropriate Backgrounds should be easy.
Although it's uncommon to make rolls involving Background Traits, your Storyteller might have you do so to see if you can obtain information, goods or favors. For example, you might have to roll Wits + Resources to keep your stock options healthy, or Manipulation + Contacts to wheedle that extra favor from your smuggler "associate." For example.
With Influence the character has pull in the mortal community, whether through wealth, prestige, political office, blackmail or supernatural manipulation. Kindred with high Influence can sway, and in rare cases even control, the political and social processes of human society. Influence represents the sum of your power in your community, particularly among the police and bureaucracy.
The system we use is simple. Through RP, down time and work with the ST's a player can increase their characters backgrounds with time and experience. As there is no hard and fast rules for this int he VtM core we use those set in Mage. 3X Current.
Though it is not unheard of to be rewarded with points in backgrounds through exceptional RP and choices the STs find fitting.