Each product should have its title and Meta description completed with 100% effort. To help you complete these fields on products that have already been entered into Magento, consider using Magmi to help you add this data to hundreds of products in one go. If your unsure how to add or modify the Meta information on products and categories then read my tutorial here.
The title attribute and Meta description are important factors for SEO, and are your first point of contact with potential customers. Aim to include targeted keywords (keywords that customers are likely to be searching for into both these attributes). You don’t need to worry about completing the Meta keywords attribute as this attribute is now defunct and not used by most browsers.
Magento is pretty functional in terms of its SEO capabilities, as it already adds canonical tags to most pages where duplicate content issues may become apparent e.g. category pages. To further enhance your SEO, I would recommend you install the Fishpig plugin to enable you to write regular content articles for your website. The Fishpig plugin eases the process of adding a WordPress blog to your Magento installation as it allows you to migrate your current theme to the blog, and is made accessible by the Magento admin panel. Read here how to setup the Fishpig plugin.