Most law firms will do some form of background check on their potential hires, but the depths of their investigations seem to vary. Virtually all firms will check with the local state bar to confirm that you are an active member of that bar. In addition, if you are currently working as an associate at a firm, most potential employers will look up your biography on your current employer’s website. Thus, before you start conducting your job search, you should confirm that your biography is 1) on the website and accessible, and 2) that it is up to date with your most recent work experience.
In addition, please note that a lot of firms are now looking up potential hires on social online networking sites like www.myspace.com or www.facebook.com. Make sure that anything that is accessible to the public is something you are comfortable with a potential employer seeing. There are a number of stories about candidates who failed to get interviews or job offers because of the types of pictures/written materials the potential employer discovered on these types of social online networks. Use these types of websites with caution.