This is Part II of Google Webmaster Chat. You may also want to read Part I.
2. Keep the number of links on your web pages to less than 100 per page.
3. Heading tags like H1, H2, H3 are a great way to organize information provide context to your content.
4. You may hide certain elements of a web page using the display:none property of CSS (like for creating printer friendly pages). That’s considered fine as long as the use of display:none is not abused to selectively hide content from site visitors while at the same time showing it to search engine crawlers.
5. I always thought that Google ignores meta tags except the description meta tag which are used to display snippet in Google search pages. However, they mentioned in the Q&A that "Google doesn’t use the meta keywords tag very much" – so the keywords meta tag may have some weight.
7. Extra CSS DIV tags in your web page won’t harm your rankings in Google.
Duplicate Penalties, Reconsideration Requests, etc.
1. If your blog content is syndicated via RSS feds, Google can distinguish original articles from syndicated content if they have a link back to your site.
2. Blog pages like categories, archives, authors can have the same content as the article. You may think of blocking Google Bot from accessing these files to prevent duplicate content issues but Google doesn’t recommend this.
3: If you have mutiple URLs for the same content within your site, each URL could be attracting it’s own links (thus diluting the link juice). It would be better to instead have one page for everyone to link to thus consolidating the value of all the external links.
4: If you site complies with the Google Webmaster guidelines but notice a sudden and significant drop in traffic from Google, it is advisable that you submit re-inclusion request. You can do so even if your site is not completely banned from the index and only a few pages have been dropped.