Good photo composition often involves some kind of correspondence between two or more elements in a photographic composition which creates a kind of aesthetic pleasure.
In the photo below, there is a striking similarity between the lacy hat on the girl and the headgear of the woman in the image on the side of the bus, and also between the trinkets and the decoration that hangs from the head-gear.
Contrasting elements in a picture are interesting too and in this photo the two faces seems to be opposite to each other - the lady on the left has a down-turned face, while the lady on the right has an up-turned face.
The red background which is the side of the bus serves to hold the whole composition together especially as it is echoed in the colour of some of the trinkets.
Above: Vendor Selling Trinkets (Dalian, China) by Anne Darling
Another composition tip is to make conscious use of the lines in the picture, whether vertical and horizontal.
The converging lines in the photo below create depth and draw the viewer into the picture.
Converging lines also help to create a sense of distance.
The dog is walking away from the viewer which also adds to the sense of being drawn into the picture.
The two boys and the dog are slightly separated from each other which enhances the composition and, although it is an informal shot, there is a sense of careful positioning.
Above: Young Boy (Inner Mongolia) by Anne Darling
Although you cannot always choose to position all the elements in your composition, by moving yourself around the scene you can still line things up more to your liking. This takes practice! And the more you practise you more you begin to spot potentially good compositions in advance.