One of the best ideas that I got when I started my newest Trail of Cthulhu campaign was the concept of the player owned “Shop”. The shop is a focal point for the campaign, as both enemies and allies learn of it and start to interact with the characters “On their turf” so to speak. It also provides numerous layers of intrigue and communally building it with my players was a terrific experience. Put simply, what it did was help get my players into the world and gave them a sense of ownership over something important to the game. This idea also works in other mediums as well such as various roleplaying games I have played like Baldurs Gate 2 with the stronghold mechanic and Shadowrun Dragonfall, where your safe house is in a small community with different NPCs who give jobs, information and so forth.
For my two Shadowrun Games I am running with Mostly Flesh and Steel (Shanghai, China) and Icarus Protocol (Tenochtitlan, Aztlan), I felt one of the best ways to give my players an introduction in how the world worked was to have an established home base. Like with the store, the players communally describe the safe house where their runners meet and generally tend to do some of their business. Adding descriptions of it, does it smell, was it used by former gangs, is it in an architecturally interesting building and so forth. To further deepen this aspect of creation, I also decided to mimic a character like perk and negatives system, so that the players could customize what services and benefits their communal hide out might offer them.