I often like to start with an interesting negative quality or try to throw together two seemingly disparate aspects of the world and see what I can come up with. Most of my better characters have come from this process. For a few examples (in 5th ed, but the principle can still apply)...
Starting with the "dry addict" quality, I decided I needed an interesting reason that this guy stopped using. I came up with a former gang enforcer who had been a kamikaze addict, but during a job gone south the Star came down on him, and, needed an extra bit of juice, he overdosed, collapsed, and was arrested. He's been recently released and has decided that drugs are crutch, and has starting augmenting himself to make up for that lost edge. Also turned to bushido for the discipline he needs to stay away from the stuff, but with a very street gang spin on it.
In another case, I wondered how you could put together a conservative Japanese background and American Indian shamanism. Came up with a young half-Japanese Shiawase citizen, who's father is a powerful executive. They manifested magical talent but simply weren't meshing with Shintoism, Wuxing, or any any of the other traditional styles of magic taught in East Asia. Wanting to explore the American half of their heritage (and being singled out in Japan for being a halfblood), they badgered their father until he caved and grudgingly got them into a university in Seattle to study western hermetic magic, though they quickly became more interested in their Amerindian Studies classes and found their totem animal, and are now putting one foot into the shadows as they try to escape the rigid academic approach of their thaumaturgical studies and try to work with their gut a little more.
