If you have ever sat and watched a painter you will see the time and effort they put in to building up an image, adding paint slowly, brush stroke by brush stroke. Photography is much like painting but I like to think of it in reverse. The art of a good picture is to constantly take things away until you have the image you are trying to paint.
When you first stop and look at a scene, the first instinct is to try to capture as many things as possible in the frame. However a photos that has lots of things can appear to be busy with no clear focal point or purpose. A good photo draws your eye in to an image moving left to right or front to back ideally directing the viewer to the main figure you want their eyes to rest on, for example a person, tree, mountain.
EXIF DATA: OLYMPUS OMD E-M1, Lens: M.9-18mm F4.0-5.6, ¹⁄₂₅₀ sec at ƒ / 18, 0 EV, ISO 200
Once you have worked out the main point of your picture, stop and look at the things that are not relevant. Is there a pole sticking out of their head? Is there a shrub that does not do anything? Is there something in the background that is distracting? Sometimes it is just a matter of waiting a few seconds for things to move or taking a step to the side or closer to remove the distraction.
Next time you are out try subtracting and see what you end up with?