set regular hours, just like punching a timeclock, put your computer in a home office that is dedicated to nothing else, and keep it a dedicated office space. get kids and others to respect your work hours, that also includes the same tactics you would use if you worked outside in an office: using voice mail and email, setting certain times to take and answer messages, not taking random calls and visits to disrupt your work time, scheduling appointments, arranging for child care if necessary.
making other appointments and demands outside of worktime, not during. Dress for work, don’t slop around in your jammies all day. don’t need a suit and heels, but make your dress and demeanor businesslike. you have to do this so family respects your time and your work. do not volunteer for things that cut into your worktime. be professional in dealings with clients, in communication–no conference calls with kids wailing in the background.