The best out of focus backgrounds are those with no definition in them at all. This forces all of the attention on the subjects. As soon as elements in the background become defined, they also become distracting. In this picture of meerkats I shot in Namibia, the sunset lighting is good, the poses are cute, and the eye level perspective is ideal, but it’s the background being so soft that makes this work so nicely. Backgrounds often make or break a photograph.
One of the advantages of shooting when the sun is low to the horizon is that it creates a natural looking catchlight in the eyes of your subjects. The eyes of the meerkats are small, but you can see that the tiny reflection of the sun in their eyes adds a nice touch to this picture.
My settings were 1/1000, f/5, 320 ISO, and I used a 300mm f/2.8 Canon lens.