One of the most common things I see in lackluster writing is describing EVERYTHING, and in a way that doesn't illuminate character.
When your main character enters a room, and you tell me what she sees, I subconsciously think "this is important."When it turns out NOT to be important, the book feels cluttered rather than carefully crafted. And by carefully crafted I mean you make it look utterly natural. (Tough job, but it's yours, sorry!)
Take for example the opening scene in Runner by Patrick Lee
Just after three in the morning, Sam Dryden surrendered the night to insomnia and went running on the boardwalk. Cool humidity clung to him and filtered the lights of El Sedero to his left, the town sliding past like a tanker in the fog. To his right was the Pacific, black and silent as the edge of the world tonight. His footfalls on the old wood came back to him from every part of the darkness.
When you continue reading you'll see that the light, the quiet, and the sound of footfalls all reappear in the story. This is not only lovely writing, we need the information for what comes later.
Description is a powerful tool. Don't waste it on things that don't matter.
While you're writing, you'll put in a lot of things you won't need later. You'll revise them out once you're done and you know what you need.