2. She Had A Life Outside Of Clark
Granted, as it is, for the most part, Superman's story, events tend to revolve around him. But the key to a great supporting character is their life outside the story; how their personality has been developed and shaped before we the audience are introduced to them, so that they impact events in a meaningful way. More than any other Lois, Durance/Lois doesn't feel like she exists only to be Superman's love interest. The first time we meet her, she's come to Smallville to investigate her cousin's death. It's explicitly clear that she isn't there for him. In fact, she and Clark initially can't stand each other. Throughout her first few appearances, plenty of the situations she finds herself in have nothing at all to do with Clark. Shes had her own relationships just like Clark has (more so, actually), and has several more after she comes to Smallville. Later on, she ends up staying in Smallville not for Clark, but in order to help Jonathan Kent as his campaign manager while he runs for senator. It isn't until later that Lois and Clarks lives come closer together and they begin to actually have feelings for each other, and this gives us time to get to know Lois as Lois the person rather than as Lois Supermans love interest.