For WordPress there are a few plugins that can really boost your Search Engine Rankings, these are generally referred to as SEO Plugins.
What you definitely will be using are the Headspace2 Plugin and also the Google Sitemap Plugin will come in Handy..
Headspace2
This plugin gives you a lot of features and you can configure it to do a lot of things automatically.
There is a small learning curve to get your head around some of the more advanced features, but start using it and you will learn while working with it.
Below your content editing field in WordPress there will be extra options for Headspace2 meta data.
In the meta date section you can change the HTML Title tag that is indexed by the Search Engines and you can change / write the Description Metatag.
And there are a lot more options! But please check you template header file that it uses the code <title><?php sbc_title (" " ); ?></title> so that Headspace2 can do its work the best way it can.
Google Sitemap.xml generator
Although it says Google Sitemap, the file sitemap.xml file is now used by all the mayor Search Engines like Yahoo, Bing and Ask, so this if definitely a must have for SEO.
You can put a link to your xml file in to your Robots.txt file for auto-discovery by Search Engine Robots.
Sitemap Generator
This sitemap is different from the previous one, since this one displays your website in a nice sitemap page that is automatically updated once you publish something new like blogposts or pages.
It is also great for internal linking to the pages with the title of your post or page (which af course holds your keywords).
Meta Robots WordPress Plugin
Robots Metadata is used to "Guide" robots through your website and send them to your most valued content.
With this plugin you can do some advanced "Pagerank sculpting" if you want, but first start by using it to Noindex,Nofollow the pages you don't want to show up in Google's index like your Login page and other WordPress Meta files.
Nice thing about the settings page is that you can edit your .htaccess file and robots.txt file from there, provide they are write enabled. Please note to make them read only for security reasons after editing.
SEO Slugs
SEO Slugs is quit a handy plugin, what it does is shorten your WordPress "slug" by removing stop words like the,it,you,can,do and lots more.
The WordPress "slug" is what is used by WordPress for creating your URL based on the setting your provided in the Permalinks option.
You can af course shorting it yourself and from version WP 2.7 upwards this option is right under the Title field, but this plugin works great so why not automate it.
Tip: Use the Permalinks option "custom" with the code /%postname%/ and set the Robots Metatag plugin to append "/" to the pages and categorie pages to be consistent in your URLs.
Feedburner plugin
Use this plugin to improve the usability and options for your Content RSS Feed.
Create a Feedburner.com account (yes it's free) and use the Smartfeed option of Feedburner to provide your visitors with a range of possible feedreader subscription options to choose from.
You should also include the mail subscription option for "Old School" readers…
Want to learn more? Then this article by Yoast ia a must read about Search Engine Optimization for WordPress!