Pond siting should take into 3 main factors direction of the sun , local vegetation and layout of the area.

Layout 

First to consider is slope , water will automatically level itself , so plan for this, ie if your pond will be on a slope no matter how small work out with a spirit level what will be required to contain the water.

Remember to check for underground services that could be in the area of the planned pond.   

Sun

On a clear day just watch and plot the movement of the Sun on the site , it does depend on what type of pond you are planning, as a planted pond requires more sun than say a koi pond, but too much direct sun will increase the water temperature and encourage nuisance algae to grow.

Aim for 50% sun on the pond if possible at Noon . It will of course depend on your latitude to do this. Using a structure like a gazebo or shade cloth can contain the effects of full sun.

Vegetation

Make sure no run off from flower beds, lawns etc can enter the pond as this may allow pesticides, herbicides or nutrients to enter the pond.

Trees can shed foliage into the pond , allow pests to sit above the pond or the roots to penetrate the lining of the pond, so it is always best not to site ponds near trees if possible. They can be good for shading on a positive note. 

Choosing the right pond filteration is the difference between having a trouble free pond or something that resembles this photo!

Pond decoration id not really necessary for the pond but more the pondowner.

Ponds have become a extension of the home like patio's and decking. With modern building products a pond can be a very stylish addition to any property as this photo shows. 

Design is in the eye of the beholder , but what as to be incoporated into a design is practicality. The filter must be accesible , lights must be easy to replace as over time the bulbs will need replacing , the water volume must be enough to sustain life and not let it turn into a stagnet mess. after all these things considered a well designed pond is very stylish and will get nothing but admiration.                 

Choose a liner type carefully as it is the hardest thing to change at a later date.                                                                        

  Aeration adds life to a pond 

Aeration

Aerating a pond with a pond air pump offer many advantages to a pond. The air is pumped down airline to an air diffuser to be released into the water.