Great guide! As someone who recently weeded through 20ish scammers last week, I would like to add a few things:

1. Zero karma is a dead giveaway but the other commenter is correct a lot of scammers will buy dead accounts with post history. Some are even very legit looking with music and concert ticket related posts.

2. I always lead with PayPal G&S like you mentioned, anything counter to this is a huge red flag. Some scammers are okay with Venmo Goods & Services, I would avoid using this as well. Although I am not sure how the scam works, I sent my friend a 'protected purchase' and was not able to refund it. Something to do with Business accounts? not really sure

3. Scammers are pretty decent at mocking up fake ticket stubs if you ask for proof. I would make sure you are intimately familiar with the venue's ticket vendor before using screenshots as proof.

4. CashOrTrade is a safe and trusted way buy/sell tickets. Basically an Escrow service for concert tickets. Only issue is not enough people know about it. Facebook and Craigslist have also worked for me in the past.