You'll get a few that are only there because they come from a certain kind of family where it's expected instead of desired and they don't take it seriously but the rest will be there to work.
Good place to sit in a lecture hall is not first row but the three or four behind that one and either just slightly right of center or left of center. It keeps you in the professor's peripheral vision instead of right in their line of sight to be called on but also will make an impression. They'll know you're there which sometimes comes in handy down the line if you need them to sign off on a class or other opportunity down the line.