For Emphasis, Less Is More.

Some Writing Basics: Inexperienced writers tend to use various techniques to emphasize all or parts of their text. Most of them are wrong and will be eliminated by your copy editor. Avoid the rush and don't use them.

• All Caps: Sometimes, titles and chapter titles are fully capitalized. Other than that, except for the occasional appropriate use of all caps within your text (e.g., BANG! or IBM) or when quoting from a source that used all caps (ugh), don't use all caps for emphasis. And while you're at it, get rid of the "Caps Lock" button on your keyboard.
• Initial Caps: In German writing, initial caps are part of the style, being used for nouns. However, in American English, initial caps are reserved for the beginning of sentences, key words in headlines (in an "up style"), and proper nouns. They are not used to emphasize words or phrases that you think are particularly important.
• Bold Face: Many writers like to use bold face to emphasize words that are more important than words that are italicized. Don't. Reserve bold face for its proper use in headings, subheadings, and paragraph or bullet lead-ins (such as I've used in this post).
• Exclamation Points:  Like a smack on the back of the head with a baseball bat, the exclamation point has its uses. However, said use should be rare. (See aforementioned, BANG!) Unless you're a 13-year-old girl, never use more than one. Got it!!!! (And I hope that hurt.)
• Italics: Last but not least, words or phrases to be emphasized should be italicized. However, beware of overdoing it. If you emphasize too many words--let's say way more than one percent--you've reached the point where nothing will be emphasized. The Publishing Pro