Scammer Due Diligence

Hi Guys, New to the site, and I hope the filter systems work on getting the scammers out of here...I\'ve been looking at some of the past threads, and this place sounds like the Wild West. Anyways, I was wondering if you could help me out... What type of questions, and investigative procedures can I do to find out whether I am dealing with a scammer or not? I know a little of the basics, ie. check domain whois (if they have a website), do a biz check (if they are in the U.S.), but what are some other ways I research a company to sniff out whether they are a scam or not? Is picking up the phone and calling the company still one of the best ways? Thanks.