Balance the composition of a photo using a bit of symmetry
To start with, pick the Rectangular Marquee tool and draw over half the image. Choose the most interesting half and then press Cmd/Ctrl+J to duplicate and place it on to its own layer.
Go to the Edit menu and down to Transform and Flip Horizontal. This will turn the half around to face the other way.
Select the Move tool (V) and holding Shift drag the duplicated half of the image across to the other side. Align the centre subjects so there’s a seamless join.
Press Cmd/Ctrl+E to merge the two layers together in one flat image. Go to Image>Adjustments>Desaturate to quickly convert the image to monochrome.