Something an artist often wants to give a painting is a "way in" for the viewer, that is a place for the viewer's eye to enter the picture plane and then travel through the painting. As you might guess, this is often done in landscapes. Sometimes it's literally a road; but it can be a stream, a flow of color, a stretch of light or shadow. For many beautiful entry ways, you might visit Julian Merrow-Smith's Postcards from Provence.
Figurative paintings can invite the viewer in as well. One interesting figurative method is eye contact, a look from a painted eye that seems directed at the viewer.
My favorite eye-to-eye painting is Georges de la Tour's The Cheat with the Ace of Diamonds. In that work, a card cheat steals a glance at you, the viewer, while pulling the ace from behind his back. Georges liked the device so much that he did it again; but this time, the card was the ace of clubs.
The Way In, 10x8 plein air oil on panel.