I have a couple of issues I'd like to understand a little better with regards to tagging. 1. How many tags should I be using per post, is more or less tags better and what are their implications with regards to the search engines? 2. Should I be using NOINDEX FOLLOW on my tag pages, if so why? I don't know, maybe I'm thinking about it too much but I'd appreciate your opinions and insights as the more I think about it the more I end up confusing myself.
Tags are used to help readers find your blog articles easier. You can add them in if you think that keyword is very relevant to your article. I think a Tag page should be nofollow indexed because having it indexed might kill of the ranking of your articles URL due to duplicate contents.
What if you are only displaying excerpts on the tag pages. Would that get around the duplicate content issue? Oh, and I presume you meant "noindex follow"
Sorry for the misplacement of text. I have never seen the impact of it if the posts are excerpted but many had the home page of their blog excerpted just to prevent a duplicate with their single post contents. Thus, I think having them excerpted is somehow a better way.
1. 20 keywords for tagging per post. I suggest you to submit your blog to del.icio.us, technorati, stumbleupon, digg, flickr, furl... 2. I suggest you to use "nofollow". This way prevents Google and other search engines to drop your blog to "zero".