Start the writing process by capturing what you see in your head with words and sentences. (This can be applied to stimuli that you see with your eyes too.) Once you have found words that represent the pictures in your mind or the stimuli before your eyes, you can then go back to add stylistic features like an introduction or a conclusion. Sometimes you will have to re-arrange your text. But who cares? What matters is that the images you seek to share are captured in words and sentences.
[Aside] We create words to represent some sensory stimuli--usually visual but also audible, emotional, tactile, gustatory, and olfactory--group of stimuli or collection of groups of stimuli. Many words can represent a visual stimuli in one context and then an audible stimuli in another. Sentences function similarly to words; however, a picture often accompanies whatever sensory stimuli we set out to show, if we show it by writing a complete sentence. The combination of subject and verb usually effects a picture. Active verbs almost always effect a picture. Ask yourself, what stimuli do I seek to capture here? What is the best way to capture it? With a word? A sentence? A paragraph? Etc.
1. What is your purpose for writing?
One big picture? One big picture and some little pictures? A bunch of little pictures?
2. What pictures do you need to achieve this purpose?
When choosing pictures, it is important to consider the assumptions (the conclusions) that your reader already holds, so you can properly assess what you need to establish before you can reveal your picture. This tenet is vital to the process of communication in general.
What assumptions do my readers already hold?
How big is each picture in this list of pictures that I want to show? Do some of these pictures belong to one of the other pictures that I have listed? Is my picture concrete? Is my picture abstract?
3. What kind of progression do I need to achieve my purpose?
A chronological progression? A thematic progression? A spatial progression? A comparative progression? A deductive progression? An inductive progression? Progression by concession? Progression by addition? Progression by repetition? Progression by example? Progression by intensity? Progression by option? Progression by emphasis? Progression by qualification? Progression by visual spur? Progression from the general to the specific? Progression from the specific to the general?
What picture are all of the pictures modifying? Is this biggest picture worth viewing? Does it have significance? Or is it just a way to hold together all of the smaller pictures? (which, presumably, do have significance to your reader) How can I fold up my pictures? Or what picture can I unfold into them?
4. How do I want to construct these pictures?
A simple sentence? A complex sentence? A compound sentence? A compound complex sentence? A loose sentence? A periodic sentence? A combination of these? Is the passive voice an effective way to show this picture? Have I achieved rhythm with my sentences? Should I mix in more phrases? Do I want to jam a bunch of pictures into one sentence? Do I want to spread them out over several sentences? Do I want to spread one picture out over multiple sentences? Do some of my pictures need multiple sentences to be captured representatively?
5. How will I help my reader find my pictures?
How will he/she know that I have moved on to a new picture? How will he/she know which pictures advance my purpose? How will he/she know where each picture belongs? How will he/she know where to put each picture?
Use paragraphs to make it easier for your reader to find your pictures and their various parts, but let words do all the pointing.