So what is overwriting?
It's describing everything in detail, making sure the five senses are hit. It's using the other character's name a lot in dialogue (I've noticed that more and more on television shows, by the way). It's making sure every line of dialogue has a dialogue tag.
Why isn't that a good thing?
It does a few things to the story. It slows the pace (more description slows things down a lot), it makes the writing boring, and the writer loses their voice in the process. The writer's voice is what makes their writing unique. It's the 'tone' you hear when you read, like the person is telling you a story. When things are overwritten, the story becomes flat.
Something else that happens is forced (and rotten) dialogue. I began reading a book that was recommended by a friend. The dialogue was so forced and the actions really off, I had to stop on page 2. Forced dialogue is what people say that doesn't fit, or they wouldn't say it in real life. Actions that are 'off' to me, are things that are overly dramatic. It doesn't happen in real life.
I don't remember the name of the book that had that problem, but here's what it was like:
She slammed her book onto the desk. "That's it. I'm through with this job." She plopped into her chair and put her head in her hands. "I'll never work again."
"Ha ha," Jack said. "You've said that before."
"Ha ha yourself. At least you have a job. Everyone should work, according to what society tells me. But I'm done."
Now, who says 'ha ha'? They laugh. And what society tells me? HUH? I can almost see this happening in a high school play.
Here's another example:
“I need him now!” I turned an inch, throwing a nasty glare to my assistant, Sam. “Where’s the man who can take care of…this.” In dramatic fashion, I waved my hand in front of the ugly sculpture. “Fix this. NOW!” I fell into my chair and leaned back. “You need to get this done. The client will be here in an hour and we can’t have this guy armless, Sam.”
“Yeah, and I haven’t been paid in two months.” He threw his clipboard to the floor. “This problem is now yours. I’m done with your drama and fixing everything for you. Jane, you’re on your own to talk to Mr. McAbree, the worst client in the world, from Scotland.”
I say to play it out in your head or read it aloud. If it sounds off, it probably is.
Have a great day!