I had a site stuck at #8 for months and went through and organized in a silo manner and within a few days it was up to #4 and then eventually #2 (#1 was one of the biggest companies in the world and a PR8)
for example if your website was about "Dogs" (let's keep it general lol)
Your Url May be MyDogBlog.com
Now within that main topic you can have many different subtopics. So now you have a category about each type of dog.
Dalmations Golden Retrievers Pitbulls Rottweiler
and then within each of those categories you will have subcategories
Food Toys Doghouses Exercise
and so on... the purpose is to build a broad base of many different subcategories that support your main topic. This lets Google know that your site is about dogs first and foremost and then you can begin ranking for longtail keywords such as "Dalmation Health Food"
I've attached an image of what silo structures look like for your website to give you a better idea.
Do this and watch your rankings skyrocket
If you have any questions just let me know and I'll give you a hand.