How do you check if a store is legit?

So, I'm curious, how exactly do you go about verifying if a store dealing in cryptocurrency or financial services is legitimate? I understand there are a lot of scams out there, so what are some key steps or factors you look for when evaluating the authenticity of a store? Are there any red flags that should automatically raise concerns? And how important is it to conduct thorough research before entrusting your money with any such business?