Another hint is to look at the URL at the top of your browser window ("http://.....). If the URL isn't the website requesting payment (e.g.
www.ebay.com) and/or if there isn't an "https" in the URL line, it's a fake.
In the case of the Ebay scam, an email is sent requesting payment for an item. The link leads you to a facsimile of the ebay sign-in page. Of course it isn't. It's just a way to get your screen name and password.
The PayPal scam has more dire consequences. Someone using your password can quickly transfer any funds from your account as well as the bank account that backs up the PPal account.
Sherwood