Professional versus Personal Accounts/Identities
Some academic social media sites allow you to link your accounts with your Facebook account. Do you want to merge your personal accounts with your professional ones?
Overly agressive privacy settings might be counterproductive for professional social media accounts, because you want certain information about you to be easily found and showcased.
That being said, don't ever put sensitive information on your social media profiles.
Don't be (or feed) a Troll!
The first contact someone makes with you might very well be online through your online persona or writings, before they ever meet you in person so think about the impression you might be making with your comments and posts.
Try to avoid getting into arguments or disagreements online, particularly with prominent people in your field.
If you do get into a debate, or disagreement, try to keep your contributions positive and polite, and consider taking the discussion to email or private messages if you want to continue the conversation.
Your Rights... and Copyright, too
Be sure to read the terms and conditions of any social media site before creating an account.
Most of the time you retain copyright to anything you create or post on a social media site, but nearly all of them have a clause that grants them a license to use your content in any way they wish.
Don't post content on social media sites that you don't want to share with the whole world.
If you want to post content, protect yourself by adding a copyright statement (or Creative Commons license) on your materials.
Respect other people's copyright rights, too. Don't post anything unless you have permission, or are allowed via Creative Commons license.
Link to items you are unsure of, instead of posting or uploading them.