Control of design must be learnt by bitter experience. Mistakes have to be made and acknowledged before images are successfully created. Eventually many elements of design become second nature and the incidence of good images increases. Take lots of pictures and keep only those that are the most pleasing.
Generally it pays to keep things fairly simple. First of all, don't try to cram too many concepts into an image or the time available. It is better to do a couple of shots well than to try numerous ideas and get them all wrong. So plan realistically and keep expectations under control. But it's not just timescales that need to be controlled - the environment itself may also be overcomplicated. If so, try to isolate interesting elements that provide meaning or context. Then consider how these relate to other features and to the subject.
In general it is wise to avoid unnecessarily complicated compositions. A simple shape or angle, or a telling look, is sufficient basis for a successful image. So keep the design as straightforward as possible and, when everything is optimized, pause for the critical moment or an appropriate expression before releasing the shutter.
Colours, lines, shapes and textures are all powerful when used as elements of simple compositions. Colours can be used to frame the subject or draw the eye into an image. Environmental shapes and lines provide depth and direction, and textures add interest to surfaces. Use simple features such as an old boat lying on a beach, as these may have more impact than visually busier elements. Try a high camera angle where nothing suitable is available. Using the ground as a backdrop helps to reduce unwanted detail.