This is a very common concern for students and their parents. Because I don't know the age of your student, I cannot be sure which strategies would be appropriate for you. Generally, younger elementary students who are learning to read can use visuals in the text to help them comprehend what the words are saying (photographs, illustrations, simple charts and graphs, examples). Younger students also ask lots of questions about things in a text that interest them or that they don't understand, which is age-appropriate.
At about 3rd grade, non-fiction text become more important to learning and students start to work on strategies to help them with comprehension. One important skill they need is to be able to identify the main idea of a text as well as the supporting details. Graphic organizers can be very helpful with this task. The structure of the text can also help. Is it a news article? Is it a biography in chronological order? Understanding text structure can improve comprehension.
Previewing the text before beginning to read can give the student important information. Look at the glossary, table of contents, and index. Check out visuals, headings and subheadings. Look at the questions at the end of the chapter before beginning to read to get an idea of what is most important to understand about the text.
If students can give an accurate retell of what they just read, comprehension is likely good. A retell strategy that incIudes the topic and a few details is common, I also like to ask students to summarize the key ideas of a non-fiction passage on a sticky note - most important points only! Teaching students to go back and re-read parts that they are not able to explain to an adult is another helpful strategy.
Of course there could also be issues understanding unfamilar vocabulary, for which context clues and word analysis strategies (root words, affixes) could be taught.
