Remember to visit the company's website to mine through what they are making public about themselves. Press releases and news are two main things to look for but you never know what to expect so browse thoroughly. Use Google's site: search to search within a website that allows Google to index all the words on the site. Here's an example.
Not all companies are equal! This will impact the availability of information.
Availability of information about a company varies.
Here are some of the major factors determining availability of information:
US Based Publicly Traded Company - Lots of Information Available
US Based Privately Held Company - Very little information available
Non-US Based Publicly Traded Company - Some information Available
Non-US Based Privately Held Company - Very little information available