Never give out your private keys and make sure you are on the actual website before entering your keys. There are so many phishing sites out there that look exactly like the real thing but are designed to steal your money from you. I can not stress enough not to share your public keys and to be sure you are on the correct site. Never click links to myetherwallet or any other wallet site (especially if the link was posted in slack) be sure the certificate is correct before entering private keys. This is a main reason I decided to get a ledger Nano s.