What species does your group tend to bump into the most? When I write adventures, I'll use exotic aliens or ones that I simply don't know that much about so that I can learn more about them, but when I'm making up an adventure on the fly or creating a spontaneous NPC for my players to encounter (shopkeepers and the like) I tend to use the same aliens again and again just because they are the most famiar to me. As such, my players tend to meet a lot of Rodians, Trandoshans, Arconans, and Twi'leks.
I'm curious if this is the same for everyone, or if I just have a severely limited imagination. What aliens do your players seem to always meet?