New camera shoots crooked photos

I'm not sure how you can easily confirm it is the camera and not operator. Maybe set up some yard sticks or something and turn the grid on. Confirm your marks are level and then line your grid up with them. Just trying to think of someway to confirm it's a camera issue.

 

Setup on on tripod, and shoot a grid (like a brick wall), remote release or timer to make sure that the act of pressing the shutter is not tilting the camera. If it comes out level, then it is operator issue.