Hold the camera straight. A picture that’s leaning sideways a bit is thumbing its nose at whoever’s viewing it. Of course, if you’re shooting an ‘atmosphere’ picture for special effect, hold it as crookedly as your fancy demands.
Straightening the camera takes only one second longer. Even if you are pointing the camera slightly upwards or downwards, so that things go fan-shaped, spend that second in straightening the camera.
And, by the way, that goes for snaps, too.