Researching companies is a critical part of winning a job offer.
There are many ways to do it, but this is my approach to it:
#1 Talk to current and old employees
#2 Get familiar with their values and mission statement
#3 Research the projects they are working on
Number #3 is critical.
Companies want people that can solve their problems. By researching their projects you can familiarize yourself with what they need and you can position yourself to be the SOLUTION -- and get hired!
Companies love to see that you've done your homework!