I'm no Paypal or eBay pro but from reading dozens of "I got ripped off" threads I would suggest considering:
1) Ask your local bank or credit union to open a new checking account and use this solely for Paypal transactions.
2) Never keep more than $20, $30, $50 whatever you're comfortable with in your Paypal account.
3) Remember Paypal is NOT FDIC insured (like a bank is) so if they out of business, your money goes bye bye.
4) Make sure to read and follow Paypal's
protection policies
5) Do not accept credit card paypal payments, keep your account a personal account
6) Of course don't share your password with anyone, etc.
7) Most eBayers are idiots and never read the auction rules