Be brutal when wading through the scammers and time wasters.
If anyone even gives you a hint of something feeling off, ignore and block.
Do not give your address out until you are comfortable.
I've been selling bits and bobs on Marketplace and it's a nightmare tbh. Most people don't read the listing properly, don't pay attention to the first half of the postcode in the listing so then back out when I'm too far away. Or they promise they are super keen and can't wait to collect, then crickets.
The best ones are people who are polite, type in full sentences, and offer to come round at my convenience.
The weirdest exchange was with someone wanting to buy some tatty old Kallax units, she didn't read the listing properly, didn't understand the dimensions of the units, and backed out because they were the wrong size. Annoying, but nothing dodgy. She then asked me to refund her the money she sent, and put her bank details in the chat. She never sent me money - I do cash on collection only. I have no idea where that came from or how it could end up as a scam, but it was enough for me to block her straight away.