1. register two paypal accounts. use one and keep the other as spare. when you sense some thing would go sour, empty the regular one and direct all new transactions to the spare account so your business is not interrupted due to account freezing.
2. do not keep a balance of $50 overnight. withdraw, withdraw,withdraw,... I know this is hard to do if you have 10 payment coming in everyday but keep the balance as low as possible.
3. know a friend's paypal account. in case something is going sour very soon and you are concerned that withdrawal is slow and paypal may stop it, beam the entire balance to friend's account. That's instant.
4. when possible pay it with visa/mc. it helps but does not guarantee you can get the money back. paypal has nasty means to recover their money from you if they cannot recover it from the seller in case of chargeback.
5. don't believe paypal spokesman's bullsh!t in MSNBC report. they WILL freeze your account if you chargeback. so that's why you want a spare account so you can continue to use paypal.