Every
client website has a
shortcominguniqueness and it's in it's domain names. It's the standard that no two websites can ever have the same domain name, and
savesame site extension name. so you may only need to check the URL and note suspicious ones.
For example
https://www.facebook.com is different from
https://www.facebook.online or
http://www.facebook.com and still different from
https://www.fb.facebook.com, so if you can learn to identify the discrepancy in the domain names
and, you're 95% safe.