I have a blog who didn't rank very well. I updated title and description tags and almost in real time I got new, good rankings for my pages. The question is: Are these rankings already definitive or could them furtherly improve at a next index refresh? I still have some pages not in top positions, so, have I just to wait for a better positioning, or should I check something else? What is in your own experience?
On today's Google, there's no such thing as "definitive" rankings. Rankings shuffle around all day every day - some SERPs churn a lot, and others not so much or so often.
There is a definite limit to what you can do on the page and on your site to help your rankings. At that point the rest of your improvement is out of your hands, at least directly - it comes from other webmasters linking to your articles.
You can help the process by creating "linkworthy" articles and networking in various ways to let others know your blog is there and might interest their website visitors. Link building is an interesting skill - and WebmasterWorld has a Link Development Forum [webmasterworld.com] where you can discuss and learn about various approaches.