What type of blog script are you using?
If you are using Wordpress, there are a lot of options that are availiable.
Some are better than others but it also comes down if you want a free plugin or a paid plugin.
There are lots of free Wordpress plugins but you can also upgrade to a Pro version with some. As with most freebies, there is another motive in the background and that is the upgrade aspect to the pro version.
One thing I must strive to you, if you have a new blog, no matter what type of SEO plugin you use you have to be patient as search engines will not put you on top just because you have good seo for the blog.
You also have to get quality high pr backlinks, social backlinks, quality contet, content added on a regular basis, and more.
One thing to rember, always seo for visitors and not search engines, they do not buy aything. Second seo for search engines.
If interested in a great quality seo plugin for your posts or pages, please PM me and I will help you out.