One of the biggest things for me is that the aliens not be total stereotypes, I'm fine with them valuing certain things more than humans, Logic, Honor, Religion, the State, but each individual should have a different understanding of what that value means. The best example for me was the Cardassians. Dukhat, Garak, Damar, Tain and Marritza all had vastly different ideas about what it meant to be patriotic and to serve Cardassia. Some of them even changed their minds. Even when they were first introduced in The Wounded, the characters were easy to differentiate from one another. Compare that to the Klingons. While there are a few that break the mold, many characters could easily be replaced with others with no changes to the story or motivation whatsoever. I want to learn about the traditions and politics of the aliens as much as we did with the Klingons, but have the variety and characterization that we got with the Cardassians.
