I'm reading a good book that was published last spring, but I got pulled out of it by an "As you know, Bob."
"As you know, Bob," is what some writers and editors call it when the author uses conversation for an information dump. "As you know, Bob, I have worked at Acme Products for 15 years now." Two characters aren't really going to mention facts both of them know in conversation. There are so many ways to do this better, from having the author simply tell us that Sam has worked there for 15 years, to Sam dusting a plaque that says "15 years of service at Acme Products," to Sam thinking "15 years of the same stale chatter, 15 years of lunches eaten on the run..."
There's a funny listing of common mistakes (some unique to sci-fi) over at http://www.sfwa.org/writing/turkeycity.html. Here are some of my favorites:
Brenda Starr dialogue
Long sections of talk with no physical background or description of the characters. Such dialogue, detached from the story's setting, tends to echo hollowly, as if suspended in mid-air. Named for the American comic-strip in which dialogue balloons were often seen emerging from the Manhattan skyline.
"Call a Rabbit a Smeerp"
A cheap technique for false exoticism, in which common elements of the real world are re-named for a fantastic milieu without any real alteration in their basic nature or behavior. "Smeerps" are especially common in fantasy worlds, where people often ride exotic steeds that look and act just like horses. (Attributed to James Blish.)
Useless ornament in prose, such as fancy sesquipedalian Latinate words where short clear English ones will do. Novice authors sometimes use "gingerbread" in the hope of disguising faults and conveying an air of refinement. (Attr. Damon Knight)
An artificial verb used to avoid the word "said." "Said" is one of the few invisible words in the English language and is almost impossible to overuse. It is much less distracting than "he retorted," "she inquired," "he ejaculated," and other oddities. The term "said-book" comes from certain pamphlets, containing hundreds of purple-prose synonyms for the word "said," which were sold to aspiring authors from tiny ads in American magazines of the pre-WWII era.
Tom Swifty (Full disclosure: my brother-in-law is named Tom Swift, and his brother is named Jonathan Swift.)
An unseemly compulsion to follow the word "said" with a colorful adverb, as in "'We'd better hurry,' Tom said swiftly." This was a standard mannerism of the old Tom Swift adventure dime-novels. Good dialogue can stand on its own without a clutter of adverbial props.