Visualization is a communication technique.  It is a very effective way to communicate both abstract and concrete ideas and has been employed since the dawn of humanity.

The key to effective visualization is the ability to create mental imagery.  Basically the message is converted by enabling the recipient to view the concept without physically seeing it. 

Maps

Maps have long been used by people to present geographic information that allows the visualization of locations, for example terrain, boundaries, landmarks.

Maps are a great visualization tool  that can be used to determine things like plan of attack (historically this was an important use), travel plans, ownership and so on.   

The key here is not the physical map (just a tool) but the ability of the viewer to create a mental image of the unknown based on the map.  This increases the likelihood decisions based on the information will be good ones.  

The Minds Eye

While tools, that is images or templates are valuable in the process of visualization the technique relies on a persons ability to “see with their minds eye”

A physical presence is not needed to actually view the object of visualization.  You may be in an empty room and see it in your mind as furnished.  Based on the mental imagery you can build a design plan that will be appealing to you without a lot of trial and error.

Not Always Easy

The technique can be very powerful but is not always easily executed.  You need to train your mind to see things without using your eyes.  This is a great skill and well worth cultivating but you will probably need to practice to create proficiency.

The first step is accepting the value of visualization and the second is focusing your mind on the concept you want to visualize.  That will get you started.