What I mean by balance is, you may have seen a photo or two, where everything is heavily weighted on one side of the frame, with nothing of significance on the other. In other words, it looks a good deal one sided.
In some shooting situations, you may not even have to give much thought to balance, but it is worth giving some consideration, when confronted with a situation where you need to place your main point of interest on or near the edge of the frame, to add another subordinate point of interest on the other, upper or lower side of the frame. For instance, a tree branch, a rock, a bird or an interesting bit sky perhaps. Making sure that this subordinate object is not going to draw too much attention away from the main point of interest. A smaller object will always balance a larger one, or a softer colour will balance a bright one.
Simply by checking the scene carefully prior to pressing the shutter button, and by moving to the right or left, or by gaining a higher or lower viewing angle, you can be more creative with your shots and they will not only be more interesting, but they will also have more impact.
Balance can be a bit like symmetry in shots. Where, if you have a number of objects of the same size and colour filling the frame, such as green leaves, you can add a brown one and by placing it on one of the Rule of thirds intersecting lines, you will not only give the shot more interest, but it will then have a focal point, a very important element.
Balance can also relate to subject perspective, or if your subject is side on to you and, for instance, looking toward your right, place the subject on the left of frame so it is looking into the scene and again with the Rule of Thirds in mind, place the subject’s eyes on the upper left part of the frame.
An non-level horizon line can also cause a photo to look unbalanced, so also be aware of that if you are shooting a scene which includes a horizon line.
If you don’t get all this quite right on the day, there is always the possibility of a bit of post production later on the computer to tidy it up.