First of all, you need to check the email address of the sender. The scammers always try to send the email with an address that appears similar to @paypal.com. You should always try to respond only to emails that come directly from @paypal.com. If the email has variations like @paypal.support.com or @paypal.announcement.com, then you should consider the email as a scam.
Consider reading the content of the email carefully. If it asks you to click on a link or reply to the email with personal information, it is a PayPal scam email. PayPal will never ask you to reply with personal information or click a link to verify a purchase. Even if you click the link and it looks like the PayPal website, don't believe it.
Consider where the email landed. Is it in your junk email? Is it in an email account that is not registered with PayPal? These are signs that it is a scam email.
Open a new web browser window and log into your PayPal account. If you have a dispute, need to verify anything, or need to update any information, you will see a note in your account. PayPal will not send you an email with a link to do something on your account, and they will not request information by email.