Check the URL

Look at the URL first (the address of the page you found).  What does the domain name tell you?  

Domain Name = Domain + Top Level Domain

A domain name is a domain, and a top level domain (TLD).   For example, the domain name scientificamerican.com says "this is the scientificamerican domain, and we are a COM - a commercial site funded by selling things.

Top Level Domains and Implications

• .com (commercial) – The most popular TLD, .com was meant to be used for commercial purposes, but is now used for virtually every cause imaginable. 
• .net (network) – Intended for network web sites, this TLD is also commonly misused for a variety of purposes. 
• .org (organization) – Another commonly misused TLD, .org was originally meant for sites that represent organizations and non-profits. 
• .edu (education) – This is usually used by colleges and other educational institutions, and it is not typically available for public registration.   
• .mil (military) – Restricted to military use only, .mil is not available for public registration. 
• .gov (government) – Restricted to government use only, .gov is not available for public registration. 
• .biz (business) –  .biz is intended for business use, but its popularity pales in comparison to the .com TLD.  
• .co (company) – A newly launched TLD, .co can be an alternative to .com but can also be used to fake a legitimate domain. 

Subdomains and Pseudo-Domains

The beginning of a URL can include a subdomain, If you saw "www.scientificamerican.com" then WWW is the subdomain, which can generally be left out.  But blog.scientificamerican.com, then this would be the blog site associated with Scientific American, and you could trust it.  

Fake news sites often begin with a pseudo-domain as the subdomain -- a subdomain pretending to be a domain. Scientificamerican.wordpress.com has a pseudo-domain and should not be trusted, but  blog.scientificamerican.org can be.  If the domain name ends in “.wordpress.com” or “blogger.com” these are personal blogs rather than news sources.

If slight variations of well known websites appear, such as “.com.co,” this is usually a sign that the website is fake version of a source. However, remember that foreign reputable news organizations may have these country-specific domains. For example, ox.ac.uk means Oxford University in the United Kingdom.