You can read more about these at SEOMoz: SEO Best Practices
Title Tag Format
Primary Keyword – Secondary Keywords | Brand
Brand Name | Primary Keyword and Secondary Keywords
Turn on core title tag and also install SEF Title Prefix and Suffix
The Usefulness of H1 Tags
H1s are important for users but not necessarily for search engines anymore.
Don’t get daft about where the H1 is appearing, could be site title, could be logo, could be articles. Just ensure you have logical, semantic order.
The Usefulness of Nofollow
We recommend using rel= for thwarting would be spammers of user generated content. We also recommend using it as an incentive for creating active users. (At SEOmoz, we remove the nofollow of profile links after the user has earned 100 mozPoints.)
We DO NOT recommend using nofollow for PageRank sculpting anymore.
Comment developers taking note? This would be a great feature, have links be no follow until people had commented X times.
The Usefulness of the Canonical Tag
The canonical tag is still young and is only useful as a hint to the search engines to prevent duplicate content. It is not the silver bullet that webmasters are looking for. (nor the droids for that matter)
If you must, stick it in your template index.php. I’m not going to bother.
The Use of Alt text with Images
We recommend including alt text for all images on all publicly accessible pages. We also suggest adding images with good alt text to pages targeting competitive rankings.
Remember something called accessibility? You should be doing this anyway. If you are not, go read Usability, Accessibility, Web Standards, SEO and You.
The Use of the Meta Keywords tag
If it is not a problem to let your competitors know your keywords and you are trying to rank highly in Yahoo, the Meta Keywords tag can be useful. Note: This is different from what we have recommend in the past.
The Use of Parameter Driven URLs (I.E. www.example.com/product?param=1¶m=2)
We donâ€™t recommend using them. If they are absolutely necessary (Due to something like an established CMS configuration) we recommend no more than 2 parameters.
Turn on core SEF, and don’t bother with the 3rd party SEF extensions.
The Usefulness of Footer Links
Use footer links sparingly. We recommend no more than 25 relevant internal navigational links.
Link schemes = bad
Make sure you are using a Joomla template with pure CSS for menus.
The Use of 301 Redirects
We recommend 301 redirects as the best way to redirect webpages but warn that they do have disadvantages.
Have you read Get Free Pagerank for your Joomla Website ?
Blocking pages from Search Engines
The Meta Robots tag (noindex, follow) is generally a better option than robots.txt. Robots.txt files are useful but should be used sparingly and only if a meta robots tag is not an option.
Make sure you have read How to Optimize Images in Joomla
Google Search Wiki’s Affect on Rankings
We donâ€™t recommend spending any time or resources on search wiki.
The Affect of Negative Links from â€œBad Link Neighborhoodsâ€
Link neighborhoods are a real thing but the affect of links from bad neighborhoods on good neighborhoods is minimal if the links are not reciprocal.
The Importance of Traffic on Rankings
The metric of visitors to a given site is not used to help determine rankings.
There you have it. Some interesting implications for SEO on Joomla websites.