You can customize the general title of your postnuke, by filling in the correspondant fields in the module "settings". The problem is that, you will have only one title for the whole website ... and that's ugly (and bad for SEO).
A solution was offered by Markwest, in order to personnalize this title, on every pages.the title tag plugin
This plugin allow you to format titles like this
HTML for Module Developers - A Discussion :: pnCommunity :: Support at your fingertips
if you want to have shorter titles like this, you can use the other unofficial version in the comments.
If you're using pnForum, it will give you title like this
You can customize the meta "descriptions" and "Keywords" of you CMS, by filling in the correspondant field in the "settings" module, but with this customisation, you will have only one "description" and "keywords" fields for all the site.
Notes : As the Search engine were spammed by overloaded keywords tags, for most of them , they don't consider this tags anymore.
You can activate the url rewriting in Xanthia, go to the Xanthia module, then check the options "use short urls", and copy paste the .htaccess file from the "doc" folder to the root of you CMS.
/!\ Be careful, live search doesn't url with more than two dashes
Notes : an improved version of the current url rewriting is available in postnuke 0.8.
Don't duplicate links in your portal, two differents links must not point to the same content. Indeed, some search engine don't like to see multiples versions of the same page on a website (that's called "duplicate content")
To avoid this, you can use a robots.txt at the root of the CMS
An other tip, "/index.php", "/index.html" and "/" redirect to the same page so you can add this rule in you .htaccess
RewriteRule ^index\.html$ http://postnuke.com [NC,R=301]
RewriteRule ^index\.php$ http://postnuke.com [NC,R=301]
In your articles or templates, try to have a structured layout with H1, H2, H3 tags.
The module "autolink" is interesting, because he allows you to create a large amount of intern links with the same source anchor, this will help to increase your rank on the given word
When you've got an important portal with a large number of pages , it may be possible some of you ranked pages doesn't exist anymore. When search engine bots come to look for this "ghost" pages, you can redirect them to the home of your website, with an "Error 404" header.
For most of them, search engine bots don't read some meta like "revist-after", so you can take them of your head tags. It will not help you, but you will have a cleaner header.
This article is a translation from this "how to" released on Postnuke-France