It never fails: you go on to check your email, and all of the sudden, you receive four or five emails supposedly from Paypal telling you that they had detected unauthorized access of your account, or that your credit card billing address is different, or something else that you know hasn't happened. Congratulations, you just got hit with a phisher. They are very annoying to deal with, but here's a few tips on avoiding falling for these traps:

1. Report every suspicious email you receive, even if it looks to be legitimate. If there is at least one tiny doubt in your mind that it's real, send it in to Paypal's spoof department, and they should be able to tell you within a couple of hours whether or not it is in fact real.
2. Watch for grammatical and punctuation errors in the email. Authentic Paypal emails are usually quite precise and grammatically sound, with little to no errors whatsoever. Phishers will usually unknowingly put in a lot of obvious grammatical and spelling errors, and will usually single-space their emails (authentic Paypal emails are always double-spaced).
3. Keep track of everything about your Paypal account, including billing and email addresses, passwords, etc. Usually, phishers will target a specific problem like a change of billing address or a new email. By keeping track of your account, you can go back and verify whether or not the information on the email received is accurate or not.
4. Watch the email address of the email received. Authentic Paypal emails have the address *****@paypal.com, but some phishers will often add in other letters or numbers to the address, like *****@000paypal.com. Also check the URL link that the email gives. All of the ones that I received from phishers had the link as https://www.paypal.com, which, of course, is wrong. Some phisher emails don't have an URL link attached, at all, while some do, but aren't in a hyperlink format. These are obvious signs that the email is fake.
5. I have never gotten an authentic email from PayPal about such security problems, so I don't have first-hand knowledge of how much leeway Paypal gives you to make the necessary changes. However, all of the phisher emails that I've received demanded that I comply within 24 hours, or else face a temporary suspension of my account. This is a good scare tactic for phishers to pressure PayPal users into giving them their account info, so if you receive an email from PayPal that gives you these restrictions, be very, very careful; it's most likely someone trying to rip you off.

Although not guaranteed to work 100%, these tips are a good way to weed out the authentic PayPal emails from the phishers. And remember, NEVER respond to ANY PayPal email that you receive; authentic Paypal emails will specifically tell you not to respond to it, whereas phishers will not. ALWAYS log onto PayPal through their main site, and not from a link, to ensure that you won't be accidentally feeding a potential phisher your account info. Good luck, and happy auctioning.