In reply to #1, the tags really are for organizing your posts into categories. Can the tags help in Google? It depends on how they help define the focus of your site. If the tags are all related to your core business they help but if you have tagged using words not related to your core business they can hinder. If your site is about real estate and PA - you want the tags (and your content) to reflect that. You do not want to have a lot of content about other general topics as that tells Google your site is not focused on real estate in PA and ranked accordingly.
In reply to #2 - no. It still all depends on the content and SEO. Frequently changing content has no automatic positive effect on search positions - in fact it can hurt. Frequently changing content only encourages spiders to visit more often to check out the new content. Having spiders visit more often does not mean your site will rank better. Now if changing your content encourages more people to link to you - that can help you. If people are not linking to you because of your new content it is really a waste of time. You may find this article I wrote on
How Often Should A Website Be Updated interesting.
In reply to # 3 - having your keywords in both titles and content is a good thing.
Regarding how often to blog... frequent blogging on your own website encourages repeat visitors and if your lucky - links to your site. Once a week should be minimum but I personally find that hard to do. Every day would be great if you want to establish a loyal following.
Blogging is really about establishing a following which can lead to some business and perhaps links to your website. The blog format istelf is not treated as "special" by search engines and not ranked any higher than any other web page.
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