How to turn off camera's follow path constraint? This question How can multiple Curves be used to control Camera movement? says that I can disable the camera from following a path by adding a keyframe and setting influence to 0 for that constraint.

So I added a circle, selected the camera then shift selected the circle, pushed ctrl-p and chose follow path.

But as you can see when I select the camera and look in its constraints, only the track to constraint is there. There is no follow path constraint. How do I see that one to edit it?
Hm, this is another "follow path". Try to make "follow path" in different way: select Curve, Shift-select Camera, then press  Ctrl+Shift+C and select Follow Path. Then chose: in constraint settings click on "Animate path" or animate "Offset" value. This is equivalent of  "follow path" via constraint.



Also, you can add a constraint from menu Add Object Constraint, but in this way you need to manualy select curve object in "Target" drop-down selector.

To remove default "follow path" go in curve settings and unclick Path Animation checkbox.