Common methods of emphasis:

Not highlighting:
* italic text
* slanted text
* sans serif font
* monospace font
* small caps

Highligting:
* bold text
* underline
* text color
* background color
* bullets or other marks
* larger/smaller type
* letter spacing

Note that some of those techniques are generally frowned upon, as they hinder readability. Especially monospace font, letter spacing and varying type size will be hard to read, as they change the letter spacing and thus cheat our sense of "word length". Colored and/or underlined text can be confused with links, so should be rather only used for them.

Resources:
* Some information available from [wikipedia article about emphasis|http://en.wikipedia.org/wiki/Emphasis_%28typography%29].
* [Emphasis on Web Style Guide|http://www.webstyleguide.com/type/emphasis.html]