I was lucky enough to attend a workshop with Donald Maass on the importance of having micro-tension in your manuscript. Just as the term suggests, this doesn't refer to the over-arching conflict or obstacle facing your main character (which you could think of as macro-tension). Micro-tension is the tension that keeps readers turning each page in that "Oh, I'll read just one more chapter before bed...oh my god, it's 3am" kind of way. It's "line by line" tension. Do you have enough micro-tension in your story? Is there some sort of conflict on every page of your novel. Every. Single. Page. Mr. Maass discussed 3 main components of micro-tension:
1) Dialogue - every interaction between two characters should involve some sort of tension. This doesn't need to be overly dramatic, such as a fight. It can be subtle and implied, but it should still be there (think Hills Like White Elephants).
2) Exposition - this is a great place to show the contradiction (conflict) between what a character is feeling/thinking and what they're doing (their actual behavior).
3) Action - while this might be the easiest place in theory to create micro-tension, you still need to make sure you have conflicting emotions in order to keep readers turning the page.
A great idea from Donald Maass: Print out your full manuscript and throw it in the air. Yeah, this might give overly organized peeps (like me) a heart attack but it's still great advice. Pick up a page at random and see if there is micro-tension on the page. Then pick up another page, etc. until you've picked up Every. Single. Page. If there's a page without micro-tension - fix it. His reason for doing it that way is that when writers read their manuscript in chronological order, they tend to over-estimate the tension on a given page. It's easier to be objective when picking a random page off the floor.
Any other tips out there on ensuring you have micro-tension on every page? Now get out there and throw those manuscripts!