Hi Steve
I'm in a very similar position to you and thinking pretty much along the same lines. What I have started doing is writing a lot of short stories. In few different genre's that aren't to far from the genre of my book.
In short stories, every word counts so you're made to write tighter. Look for competitions, check out the market lists here on Fiction Factor. There are plenty of places to submit short stuff. It helps thicken up your skin to. Rejections are a part of our life, I think.
Critiquing other writers work also helps you recognise what's good and what's not. Critters is good for this as is Absolute Writers.
I'm also looking into courses. Not many free ones that are of any use but depending on where you are, communtiy colleges or TAFE as they are called here in Australia, do some low cost one's that look interesting. I'm also looking at going back to Univercity next year to do a bigger course - more indepth but bigger cost.
One last thing I'm looking at is http://www.thomsoneducationdirect.com.au/index.cfm?id=317
Although aimed at copywriters and proof readers, it still looks at the mechanics of tighter writing.
Above all else, keep writing. Practise is the only thing that will really hone those skills. Reading, courses and critiquing helps but only you can make the changes to go the next step.
Good Luck
BT