Basic question: What is style?
Short answer: Style is the WAY you write. Think of it as the way you clothe and accessorize your writing.
Do you tend to write lengthy paragraphs or short? Do you overload with descriptions or lean toward the skimpy side? Are sentences clipped and to the point, or do you tend to be more round about?
One quick way to check out your style is to print an average page of your manuscript. How's your "white space?" I like my page to look pretty ragged. Big, honking paragraphs are a bad idea. I'll compare it to a meal. You sit down at a restaurant and the waiter brings you a steak the width of a dinner plate and the thickness of your thigh. And you have to eat the whole thing. Now, this might be a mighty fine piece of meat, but you'd still feel completely overwhelmed. By the time you finished it, bloated would be something you'd passed two hours ago.
Now, imagine that the waiter brings you a nice sized, bacon wrapped fillet Mignon, sauteed veggies, and a side of your favorite potato.
How do you eat it?
I'm betting you don't polish off one item at a time. Instead, you trade off between the three. It's the same way with your writing. Mix it up. Give your reader some description mixed with action (Sara pressed her wrinkled, tobacco stained lips together.)
Tension is like seasonings. Add it to everything. Each page, each paragraph has to have tension. If it doesn't: add it!