How do you check if a website is safe to buy from free?

I'm curious, how does one verify the safety of a website when making purchases without having to pay for any additional services? Is there a reliable way to check for security features and customer reviews without relying on paid-for verification tools? Are there any telltale signs that could indicate a website might not be trustworthy? And if so, what specific measures should one take to protect themselves from potential scams or fraud?