Here's a little writing mistake that I find is easy to make:
Forgetting about the setting.
Sometimes I lay out the setting at the beginning of the book. I throw in all those great details to show the reader where we are...
...and then I amble along (or ramble along) with the story and forget to remind the reader about the setting - to toss in more sensory details so the reader can still see where she is.
So - don't forget to remind the reader about the setting.
It doesn't have to be anything major.
One little sentence.
One little phrase.
Just enough to keep the reader grounded in the place and time.
I just finished writing a scene that takes place in the main character's bedroom.
The reason he is in the bedroom, instead of being outside where he really wants to be, is because it is raining.
And not just rain, but a thunderstorm.
But I got all caught up in action of the scene in the bedroom...
...and I forgot that it was storming outside.
When I went back and added the rain pattering against the window and the thunder rumbling in the distance - the whole scene came alive and reconnected with the previous scene in the story.
So - don't get so caught up in the action of the story that you forget about the setting.