Light can be tricky to deal with. Too dark and everything looks flat and detail is hard to make out, too light and everything looks washed out and colourless. Even in perfect light conditions, photographing into a strong light source such as the sun can often result in a less than pleasing image. The problem is that the camera's sensor is fooled into thinking that that the whole image is very bright so it reduces the overall exposure to compensate. This means that any parts of the scene that are in shadow or close to you will appear much darker than they were in reality. Overcoming this is tricky but with a good quality light meter you can often compensate sufficiently to achieve a good photo without any need for post-processing. Without one, and if you have a good quality DSLR, you can often use the camera's histogram feature to help compensate as this gives you an indication of what effect changing aperture and speed will have on the image. Failing this, you'll probably have to deal with the effects of light in post-processing.
The photo below is an example of how a strong light in front of the lens, in this case the sun, has darkened the whole scene by reducing the exposure sufficiently to make sure that the very bright parts are not overly dominant.
To overcome this problem, we need to establish what we would like the photograph to deliver in terms of colour, light and dark, content etc. Because this photograph was taken with a full-frame camera, the Nikon D600, we have a lot of information to work with and despite the problems of under exposure of the foreground, we can be pretty sure that a lot of detail has been captured and just needs to be teased out.
The first job then is to try some global enhancements e.g. to play with exposure, contrast and light. Because the sun and clouds are dominating the overall scene it's difficult to push any of these too far without starting to lose the definition in the clouds which in this scene, are a nice aspect of the photograph. This forces us to look at using a mask on the under-exposed areas of the photograph which here is about the lower 1/3rd of the image. By applying a mask to this area we now have the opportunity to modify the light, exposure and contrast, as well as the colours of the areas that currently look dark in the top image, ie the bottom 1/3rd. Again I used Cyberlink PhotoDirector 8 for this job although any good photo editor will have the exact same tools.
How much detail, light and colour you wish to add is a personal thing. Personally, I like the concept of a moody, brooding sky with subdued colours throughout but by using a mask, you can really achieve almost anything as you can control exposure, contrast, saturation, light, hue, clarity, enhance shadows, blacks, whites and even pull up or subdue the midtones in the image.
Once the mask has been used to attack the areas most needing work, you can then look at some final global corrections to further enhance the image. For example, you might want to increase the aqua saturation or lightness of the pool water or the make the blue parts of the sky a little darker or lighter. This is also a good time to look at cropping the image to just include those parts of the scene you want included. There's no right or wrong with regards editing , it's all about what you as the photographer want to achieve. Here's my take on the same image with a little post-processing.