If you are note sure if your blog posts are in the Google supplemental index, here’s a quick way to check. Go to www.Google.com and enter in site:www.yoursite.com *** –sjpked. Of course replace the your site.com with the correct URL.
One of the big reasons that blog posts routinely go to the supplemental index is that there are simply no links to them raising their page rank. Part of this is due to the way that blogs work with posts going onto a home page and then moving into the archive based on your settings.
One way to help keep your blog out of the supplemental index is to link to specific blog post pages from your website. If you point to a page specific URL for a post, not just the home page of your blog, and start to keep updated links to pertinent information, this may be one way to keep your posts live in the main Google index. Obviously another way is to write great content that others will want to back link on your blog, but if someone links to you and when, you can not control.
You may want to consider doing a special post archive on your website pointing to really hot property blog posts or ones that you particularly want to point out. What I do is to point to specific posts using Feed technology on my own website. I use a tool called FeedrollPro to allow syndication of my content and then I use FeedHoster to easily update my site feed online. This makes it super easy for me to show important headlines on my own personal website as well as to feed what I consider important content to others who are syndicating my content.
Staying out of the Google supplemental index is important so try some of these suggestions to see what may work for you too.