How do you look up if a website is legit?

I'm curious, what's the best way to verify if a website is legitimate? Is there a specific process you follow to ensure you're not putting your personal information or finances at risk? I've heard about checking domain registration, looking for security certificates, and reading user reviews, but I'm not sure where to start. Can you walk me through a step-by-step process for conducting this kind of due diligence?