One person dressed differently from everyone else. One colour that breaks the palette. One face going the wrong way in a crowd. One building out of scale with its neighbours.

The eye is drawn to anomaly. Find it before you raise the camera.

Watch for: the difference needs to be clear in the frame. If you have to explain why this person is the odd one out, the picture hasn't worked.

Try this: Find a uniform background first, a crowd in dark coats, a row of identical houses, then wait for the single break in the pattern to enter it. The anomaly only reads because of the sameness around it, so build the sameness first.

The point: visual tension comes from contrast. Anomaly is contrast.