Structure, in this context, means how a sentence is built up or constructed.
The following are some features you may notice while reading.
When single words, or groups of words, are repeated.
If a list is present, look at the order in which the points are listed. If they lead up to the most important item at the end, there is a build-up to a climax.
Short sentences may be used to build up tension. Longer sentences may be used for explanation.
Questions and rhetorical questions might be used. An exclamation such as
How amazing! can be used to indicate a strong emotional reaction.
Where the normal word order is reversed, usually in order to place emphasis on a particular word.
Individual words or groups of words can be placed side by side – in juxtaposition – to stress the contrast between ideas.
Where extra information is included in the middle of a sentence, contained within dashes, brackets or commas.
Where three dots (...) are used to indicate something more could be added.
Punctuation is often key to sentence structure. There are many possibilities for punctuation that can help you with sentence structure.
A colon (:) or single dash (-) can be used to introduce an idea, a list or an explanation. A semi-colon (;) may show contrast in the ideas before and after.
Use of question marks is always worth consideration. Questions may be rhetorical, but not always.