Classroom -- unless I don't like the class and it's super-easy I like to sit in the front center. Partly because I'm so easily distracted and partly because I'll take all the brown-noser points I can get.
Movies -- about a third of the way back and toward the center if it isn't too crowded.
Restaurant with SO -- usually across from. I let him face the window so he can look at the cars and I face the room so I can look at the people. He doesn't hear real well and doesn't really like interacting with people so I can also run interference for him that way. If the kids are with us, we're more concerned with making sure everyone fits comfortably and that the kids that don't get along as well are separated than we are about where we are in relation to each other.