Avoiding scams
Most of it comes down to two habits.
Deal locally, in person
Meet the person. Look at the thing. Nearly every scam that works on classifieds sites depends on the deal happening at a distance, because distance is what stops you noticing that the flat, the car or the tickets do not exist.
Never send money to someone you have not met
No genuine seller needs a wire transfer, a gift card, a cryptocurrency payment or a holding deposit before you have seen what you are buying. No genuine buyer sends you a cheque for more than the asking price and asks you to refund the difference. No genuine landlord is abroad and unable to show you the property.
What we do at our end
Every listing and every reply is scored before it appears, and posting requires a confirmed account so that behaviour follows people around. That catches a great deal, and it will never catch everything — a filter is a reason to be less worried, not a reason to stop being careful.
If something looks wrong, use the report link on the listing. We read them.