There are several common ways to emphasize a word in text in an email or chat message. The least desirable way is with capitals, which indicates
as rude as real shouting.
This is VERY HARD to understand.
A good method of emphasizing words is to use stars.
This is the *funniest* movie he's made yet.
You can also use underscores to indicate underlining:
That is _exactly_ what I thought!
Quotations are the standard punctuation for titles:
My favorite book is "Lord of Light".