This is a list of quick checks:
URL - A quick look at the url will give you a rough idea if the site is legit, e.g.
- Check for HTTPS (if making payments)
- Check the spellings (cococola.com surely cannot be legit)
This is not conclusive, look for other red flags, like spelling mistakes or broken links on the site. Also do the check suggested by Amos.
You can also do a WhoIs to check the owner of the domain. As an example, I did a WhoIs using the following: http://whois.domaintools.com/cococola.com
>>to my surprise, the cococola.com example I used belongs to Coca Cola.