How can you use emphasis in a sentence?

Answer 1

You can use emphasis by manipulating punctuation, ie: use of commas, semi-colons, colons, exclamation marks.

You can also use a variety of sentence structure, long and short sentances, subject/noun reversal.. etc

Answer 2

Answerer 1 did great. You can also use italics, underlining, or dashes. When I write plays I often use italics or quotation marks to set off a word or words that I want the actor to emphasize. Here is an example of using dashes for emphasis:
When she bought the sofa--all-leather, too--she got herself a real bargain.