Google Panda was introduced on February 23rd 2011. It was a very big deal. In essence, Google wanted to filter out low-quality websites and promote high-quality ones.
A lot of websites got affected by Panda. And a lot of legitimate websites got penalised too.
In essence, Panda was all about content quality. When a site is affected by Panda, the whole site tends to be affected. So what do you need to look out for?
A thin page has little content on it that can't be found on another page. It doesn't mean that pages need to have lots of text, although pages with little text are more likely to be 'thin'. Having the odd 'thin' page is not going to affect your site, but having a good portion of 'thin' pages is more likely to be penalised by Panda.
Google supplies special tools to check whether your site has duplicate content. This is a very good place to start. Duplicate content is any content that is pretty much the same as another page - whether on the same website or on another website. When duplicate content is found, Google's algorithm works out which one is the more authoritative and penalises all the rest. It used to be okay to copy text from another website and add content to your own. That's not possible any more. The bottom line is, re-write everything so that there's no duplicate content - and if you can't do that hire a professional who can.
High-quality content is better than lots of content. By all means blog about what you do, but if you haven't anything more to say it's better not to say it.