It can feel really satisfying to walk away from an office the last day of your job. For whatever reason, that job was no longer right for you and you moved on, starting fresh somewhere else.
If you didn't like your former boss and co-workers, it can be tempting to permanently sever the connection. But most of the time, even if they weren't your best buddies, it's best not to do that. Old colleagues and old bosses can be a network that lets you know about new opportunities and give you references that help you get the job. Keep in touch so they'll keep you in mind when these new opportunities arise.
Connect on Social Media
Connecting through social media is an easy way to keep lines of communication open, especially if you simply want to make sure you have a way to contact them if you need to.
Connecting on LinkedIn is better than connecting on Facebook for professional contacts when you don't want to share your personal life with them. Because you can contact second-degree connections on LinkedIn, connecting your profile to your former boss and colleagues gives you direct access to additional professional connections that can help a future job search.
Celebrate the Holidays
Sending a New Year's card is a painless, once-a-year way to remind former bosses or colleagues that you exist. Take the time to write a brief note on the card. It makes it personal and is a chance to update them on what's going on in your professional life, and let them know if you're open to new opportunities.
Send Useful Updates
If you want to take a more active approach to keeping in touch with old bosses and co-workers, periodically send them useful updates. You'll want to let them know when you've moved or had other significant life events, but if you really want them to keep you in mind professionally, send them links to professionally relevant articles. Make sure the links you send are useful. Try to find a timeline for sending material frequently, but not so often the recipient is being bombarded by mailings from you.
Whichever means you choose to keep in contact, don't be oversensitive to whether you get a reply or not. People are busy and may not acknowledge your notes. That doesn't mean they are snubbing you, or you should terminate communication. As long as emails don't bounce back, they're being received, and your goal is achieved.