http://www.yatishmehta.in/seo-for-octopress

head.html

<meta name="author" content="{{ site.author }}">
{% capture description %}{% if page.description %}{{ page.description }}{% elsif site.description %}{{ site.description }}{%else%}{{ content | raw_content }}{% endif %}{% endcapture %}
<meta name="description" content="{{ description | strip_html | condense_spaces | truncate:150 }}">
{% if page.keywords %}<meta name="keywords" content="{{ page.keywords }}">{%else%}<meta name="keywords" content="{{ site.keywords }}">{% endif %}