I saw a post from Hodderscape, which recently held a open submission call, providing writing tips from editor, Anne Perry. I thought her approach was very useful and simple. Reading slush opens your eyes to lots of things.
I also saw recently some tips on developing character from the amazing Angela Slatter, which I thought were useful too.
A while ago now I did a series of posts based on my observations on slush pile reading and the things that I saw there. These posts are probably a bit more indepth and perhaps a bit more muddled than the two recent posts I saw on the web.
Below are the links to these.
Anne Perry here.
Angela Slatter’s post here.
And a few posts from reading for Angry Robot and their first open call.
Blog post one here
Blog post two here
Blog post three here (which is on common issues with manuscripts) thoughts on blog post three here. Wherein I elaborate on issues with MSs.
Blog post four was on query letters and synopsis here.
Donna Maree Hanson, Author, Phd in Creative Writing 
This is good reading, thanks Donna, particularly your insights into the Angry Robot submissions. I tossed a story (unsuccessfully) into the ring for Angry Robot, Hodderscape and Gollancz last year, so was really curious what sort of approach the publishers might take with these windows.
Its so hard to get noticed. Publication opportunities are few between. You can only do your best.