Clarity and Focus (it's so important I feel like putting it in fancy font). Here are some examples of rejections from 2009...
You are a good writer, but I found this story too confusing in the beginning. I think you need to concentrate on the focus of the story, i.e., what are you trying to say? (Abyss & Apex)
This had some evocative description, but I hadn't the faintest clue what was going on during most of it. (Every Day Fiction)
The details and ideas are marvelous, but we spent a bit too much of this scratching our heads. (Shimmer)
I took several hits on the head re clarity before I sat down to tackle it, we're still mid battle I'm sure, but I'm hoping to have sorted the beast out before 2010 makes me another year older. 2009 has provided me with quite a lot of valuable advice in the form of rejection letters, but I think the below is the one that really struck a chord and left me with a eureka moment (we've all had those, right?)
Some great potential to the premise, but all of these interesting ideas (wings! 10,000 years of waiting! dead father glowing!) are thrown out and then left hanging. Take the time and write the full story - it sounds more like the plot of a novel than a piece of flash fiction. (Every Day Fiction)
I swear the above made me pull up my socks to my thighs, which is quite an achievement for ankle socks.