WordPress SEO by Yoast is widely considered the number one SEO plugin for WordPress today. In the past there were many other options available. Including All-in-One SEO.
But in recent days and months Yoast has updated the plugin to allow you to take advantage of all the new features the search engines have set up. Most importantly is Google Authorship.
By following this how to setup WordPress SEO by Yoast video, you will be able to follow along step by step and get your plugin running very quickly.
And another great benefit is that once you get this done on one site. You can export those settings and import them onto any other sites you create. This really speeds up the time from getting a site setup, to actually writing content.