Use a typeface for some words of some text that is different to the typeface the rest of the words use.
This technique both highlights the words set in the "different" typeface, and communicates something to the reader. In the example below the word "angry" is set in a typeface that's supposed to represent the emotion anger. Emotions aren't the only reason you might do this. You could use a different typeface because the word represents a brand and you're using the typeface that belongs to that brand, for example.
Typefaces that are set in the same size in terms of number (e.g. 20px) are often different sizes visually. You might need to play with the size of the text set in a different typeface until it looks at home in the text that surrounds it.