Before we start taking a look at some of the best SEO extensions available for Magento, we should quickly cover their installation.
Most free Magento extensions will be available to install through Magento Connect (http://www.magentocommerce.com/magento-connect/).
Paid extensions usually require manual installation; it is therefore important that whoever is installing the extension is familiar with FTP. Most of these types of extensions come with their own set of instructions, and thanks to the automatic setup scripts within Magento, there are never any complicated database adjustments to make.
Generally speaking, the most common problems with extensions can be avoided by making sure that we do this:
Check that the extension is compatible with our Magento platform (Community/Enterprise/Go)
Check that the extension is compatible with our own Magento version (for example, CE 1.7)
Disable Magento compilation prior to installing our extension
Make sure that our folders are writable...