I thought I would share the the different ways I have been determining a site's viability and if it is a scam or not. At first, I was typing the name of the company and then the word review. Unfortunately, some of the names were keywords and I was having difficulty calling up the actual company.
If a company has a history, then there is a strong chance someone may have already filed a complaint against them:
http://www.ripoffreport.com/
If not, to check how new a site is and how reliable it is:
http://www.scamadviser.com/
Thirdly, in the search bar type "who is" then the site name. This will come up with different sites which will show the domain history of the site and who owns it.
For actual people responding to Craigslist ads or advertising on Personal Assistants it is a little more difficult but doing a search to see if the facts line up would be my first step. If you do subscribe to a people search, this may help you eliminate many. If it seems to good to be true; it is.