Also, a couple other notables about omniscient --
When you dip into the thoughts of the character to show what they're thinking, you have to make a subtle transition before doing it; otherwise it'll end up head hopping. The transition is usually a single sentence that either shifts it back up into camera view for an instant or a line of dialogue that ties to the next paragraph. Also, from my observations of reading stories with it, it doesn't switch back and forth rapidly, like:
Paragraph 1: Mary's thoughts.
Paragraph 2: George's thoughts.
Paragraph 3: Mary's thoughts.
Paragraph 4: George's thoughts
It's more like:
Paragraph 1: Narrator
Paragraph 2: Mary's thoughts
Paragraph 3: Narrator
Paragraph 4: Narrator
And then, eventually, when the story dictates, it slips into George's thoughts. It might even be a couple of pages before it dips back in again or not until a later chapter.
It's tough to write slipping into the thoughts because you really have to pay attention to pacing and transitions so the change makes senses, adds to the story, and doesn't jar the reader.
Another notable is that omniscient is distancing. In order to do omniscient, some of the phrasing lends itself to distancing. I critted a piece where the writer did a thriller in omniscient and it was so distancing that it actually pushed the reader away. I wish I'd saved it now so I could study why that happened. The phrasing is difficult to write, and it's easy to slip into third if you're writing in a hurry. But, oddly enough, it can work really well for some types of humor.
It's also easy to use "was" a lot, so you have to be alert for it and try to find other ways to write the sentence.
Omniscient works particularly well for fight scenes, where multiple characters are involved. You'll see it a lot in thrillers, particularly ones with a lot of action and other things going on.
Some additional examples of books and writers in omniscient are Vince Flynn, Terry Pratchett, Clive Cussler, W.E.B. Griffin, and a new release called Legend. Even the Harry Potter books are written in a form of omnscient--the openings suggest someone is sitting down around a fireplace telling you the story. Bernard Cornwell also has done some of his books in
omniscient, thogh you'd have to look at the book before you got it--some of them are also in first person.