What are some precautions one should take when signing up for services online?

Almost every online service provides a Terms of Service and Privacy Policy (TOS and PP) which a user should be familiar with before signing up. A user should always use a strong passphrase and never share it with anybody under any circumstances. The user should also be sure to use a valid email address with a service that provides some kind of spam protection. Finally, the user should always be sure they understand how to close their account should they later decide to do so.