Never open any Email whose sender, you are not well aware of it.
Always Verify the Sender Address before you open any Email.
Never Reply to any UnAuthorized Email.
Never Click a Link in Unknown Mails as a Click on a Link is enough to hack a Web Browser.
Always Scan Attachment with a Trusted Source Software.
If Possible, avoid Forwards and Replys and write a Fresh Mail Instead avoiding Emails to Spread through Forwards.
Also do not disclose your Personal Information in your Digital Signature, the section at the end of every outgoing mail.