Starting a new WIP after years of mud-wrestling an old one is a very educational process. I highly recommend it as an exercise if you're stuck, even if you only write a few chapters. Don't, don't, don't develop a habit of always starting new things - that isn't the way to stardom, my friend! - but you just might find that the change in prespective will highlight strengths and weaknesses that you were missing while you were busy pulling out your hair. You were learning and progressing in your craft while you were on that treadmill, after all - because now you'll recognize problems as they occur. For instance....
The endings of my scenes are weak. Sometimes they just progress until the business seems to fizzle out, and I'm left with only a few blank lines to signal a change in time and place.
Elizabeth Lyon, in her book A Writer's Guide to Fiction (Perigree, 2004), discusses this. Specifically, she mentions Jack Bickham's list of possible endings for scenes (page 174):
1. discovery that a newly begun task is more complicated than expected
2. learning a disturbing piece of information
3. arriving someplace new
4. meeting someone who will significantly alter his or her (your pov character's) life
Ms. Lyon adds also that there may be a dramatic event that provides a good scene ending.
Of course these things are present in my writing, but I have a tendency to put them at the beginning of a scene: action or event - character response - fizzle. I see that I need to structure scenes this way, instead: character response - action or event. This creates momentum, as opposed to a limping, lurching pace. A resounding smack on the forehead for me. Go figger!
In addition, the first and last sentences need to have punch, impact. I knew that, but I haven't been making an effort to relate one to the other by using language to reveal parallels or contrasts. It makes a very satisfying, round shape when you can pull that off. Another thing to work on!
Now, writers who may be doing me the honor of reading this, please do add your own comments on scene endings!