Make a list of key terms used in your presentation or writing outline. Look for terms in this list that could have multiple meanings. For example, terms that have multiple meanings include "present" (the current moment, or a gift), "book" (to put on a schedule, or a thing that you read) and "liberal" (believing in freedom of the individual, or not being strict). Also, look for pairs of terms that are close --- but not identical --- in meaning. For example, the terms "conservative" and "traditionalist" are similar (both relate to respect for authority and the status quo), but the former term refers to a political view, whereas the latter refers to a religious view.
Write the definition of the term for which you are making a distinction. If you are comfortable with your grasp of the term, write this definition from memory. For example, if you feel comfortable defining the term "liberal" from memory, write a definition like "political ideology based on individual rights, freedom and social equality." Otherwise, refer to a recognized dictionary (e.g., Webster's). If you are making a distinction between two similar terms, write the definitions for both terms and underline the part of each definition that differentiates one term from the other. For example, in distinguishing "conservative" from "traditionalist," underline the word "political," since its political nature is what makes conservatism different from traditionalism.
Read over your notes and look for all the places where the term is used. Ask yourself whether there are unique factors that influence how you can interpret the term in this context. For example, imagine that you have written the term "fascism" in an article about World War II. While Fascism is not conceptually identical with Nazism (Nazism had other elements), a discussion of fascism in the context of World War II should mention Nazism.
Draw your readers' or listeners' attention to the fact that a key distinction is about to be made. They should pay special attention to the important distinction because it will influence the meaning of the content.
Articulate the distinction that you want to make. Clarify the definition of the term (or terms), referring to either a dictionary definition or a definition that suits your purposes. If you are distinguishing one term from another similar term, provide both definitions as you highlight the difference between the two terms. Mention examples that highlight why this distinction is so important to the content you are delivering. For example, when you give a presentation on money, mention cases where failing to understand the distinction between "investing" and "speculating" has caused people financial loss. Then, explain that investing is about putting your money in an income-generating asset for the long term, whereas speculating is about trying to make a quick profit. As an example, you can mention that pension funds invest, whereas day traders speculate.