There are three areas of the photo to consider when shooting wildlife; the foreground, midground and background. All three must blend together around the main subject of the picture to create a harmonious image. Things in the foreground should be well out of the depth of field or else they can appear distracting. Foreground elements should blend with parts of the mid or background. Out of focus grasses, branches, flowers or some aspect of the animals environment make up the foreground. The midground is mostly your subject but should also contain some of the grasses, branches, flowers or whatever environment the animal is in. The midground is in focus with the foreground and the background blurry around it. The background being out of the depth of field should contain colors that blend well with the two front layers. Slightly out of focus elements of the environment in the background help create harmony with the mid and foreground.
Who you are taking photos for will determine how you choose your subjects. If you are shooting solely for yourself and want to shoot every living thing you see that is fine, but if you are trying to sell your photography you need to be more selective with your subject. Choose vibrantly colored animals or large and impressive ones, they have more sale value. Pictures displaying dramatic behavior are also coveted. Basically try to capture unique or compelling photos that bring new light to old subjects.
When shooting wildlife portraits you want to use a fast shutter speed to capture the animal and prevent blur caused by movement. You also want to focus on the animals face, in particular it's eye which should be wide open, clearly illuminated and show a small twinkling of natural light.
Photographing group portraits of wild animals presents problems since there are many subjects to capture. Having a main subject and using the other animals as support can work well unless you are shooting two creatures. With two animals try to shoot ones that are around the same size and are engaged in similar behavior.
When lighting a wildlife portrait the standard is to utilize early morning or late afternoon front lighting. This low light will illuminate your subject and won't blow out your picture with too much light.
All these things will help create a more stunning image of the wildlife you are trying to capture a portrait of.