This is what I use, from reading what others have done.  Others with more experience may provide even better advice, and you can probably find other methods in the FAQ for Newbies discussion.

1.  Use Google Images.  I launch Google Images in a separate window and then drag an image from a website into the image search bar.  You will be able to find where on the Internet this image has been used, which may lead you to conclude that the image belongs to someone else and that the ad is fake.

2.  If the ad has a phone number, use Google to search for the phone number (use the format XXX-XXX-XXXX when searching).  Google will find wherever else this number might be used, which could also help turn up other ads/providers using this same number.  This could set off some red flags as well.

......I noticed a few visitors who came and pretty much stayed like 2 months lol