The topic of using italics came up in my writer's group last meeting. Specifically, we were discussing the merits of using italics to indicate the thoughts of the character. A typical passage:
"Peter turned to face the monster. Unbelievable, that thing has enormous fangs! He gulped and picked up his sword."
Some writers, such as Terry Pratchett, use this method selectively and with some success, while others, such as David Payne, use it extensively and not with great success.
I started to use italics as thoughts in writing, but after I read Payne's Back to Wando Passo, his excessive use of italics felt cumbersome and I never bothered to finish the story. It even encouraged me to go back and rewrite my novel to remove the italics.
I have noticed that the usage of italics for thoughts is slowly becoming more common in fiction, which leads me to ask this question: how do agents/editors view italics as thoughts? Is it discouraged, encouraged, or do different people have different views?
This is really more of a stylistic question than a publishing question, but as a writer myself currently entrenched in editing my second novel for publication, I'd be happy to give my opinion.
As writers practice their craft, they experiment with different techniques with language. Most people who write constantly experience fads, where they like a concept (such as using a lot of italics to indicate inner thought) and use it to the point of overusing it, at which point they might realize what they're doing and stop. This usually comes from some recent external influence. From ages 13 to about 15 I was really into ...s everywhere to indicate the pacing of the sentences because I was reading a lot of fanfic writers who were doing it. It was an embarassing phase for me, but I learned from my mistakes. Also, not all of my experiments have been mistakes. Some legitimately entered my style as a common technique.
If you find something new and you like it, have fun with it, but be aware that you shouldn't overuse it, especially if it's grammatically incorrect.