Doing business through PayPal takes a mix of common sense and experience. I previously owned a mobile phone unlock code business where I was bringing in about $30k/month through PayPal. Luckily, the majority of what I was selling came from a mathematical algorithm I had, so if I lost a charge back for some reason, it wasn't a huge deal. HOWEVER, there were some services that required me to source from a third-party and therefore required me to make an initial investment to fulfill the customers' orders. Some of the same tactics I've used can be applied to selling domains.
If you're selling from a website that has a contact form, make sure you're recording the IP. If the IP comes from Pakistan but the buyer's shipping address is in Toledo, Ohio, there's cause for concern.
If there's any hint that the buyer is shady, even after you received the payment, wait 24-72 hours before you transfer the domain. If the account or credit card they're using is stolen, PayPal will likely be notified in that time frame. Therefore, you're not transferring the domain and then getting the chargeback. The buyer wouldn't be able to open a dispute simply because you haven't transferred the domain, yet.
Ship the buyer an invoice via USPS, FedEx or UPS and pay extra for signature confirmation. Once you get the tracking number, make sure to add it to the transaction on your PayPal account.
If you have a website, be sure to have a Privacy Policy and well worded Terms of Service that specifically states the terms of use for PayPal transactions as well as a return policy. I realize that the average user will never read it, but PayPal will.
Keep records of EVERYTHING. If you ever have a dispute, provide EVERY detail, as if you were wrongly accused of a crime in a court of law. If you're on the up-and-up, PayPal will likely side with you.
In my previous business, the average ticket was around $10 so doing things like mailing invoices wasn't always worth it. When the ticket was higher, like $100 or $200, you better believe I was spending 2 minutes of time and $10 to mail out that invoice. Believe it or not, it's actually easier to win disputes as the seller through PayPal than through a credit card merchant processor. Unless you're doing business with someone you can completely trust, like the CEO of a well-known company, it may make more sense to use an Escrow company. But if you're doing lower value transactions, PayPal is hard to avoid using. Either case, I hope this helps.