It's Hard to Avoid the Con-Artists

Did you receive the info via spam?

Unsolicited  email is illegal and no reputable company would advertise this way. Avoid companies that spam.
 

Does the marketing look professional?
Is the website or printed material professionally designed, or does it look like an amateur made it on their home computer?
 

Is it a well established and respected company?
You want to purchase from a company that has a successful track record of satisfied clients who have provided true testimonials to the effectiveness of the product. ProSolutionPills, ProEnhance, Penis-Health, and SizeGenetics are highly recommended by US.

Does the site have a sensible URL?
Avoid sites that have URLs that seem designed to cram in every word that a search engine may look for. This type of company (or more likely individual) is usually just looking to make some fast cash and has not dedicated the research to developing an effective, safe product.
 

Have you seen the text on another site?
If the text on a site seems to be a copy-and-paste from somewhere else on the net, then their validity is called into question. The exception to this is that many sites may quote the same medical articles.
 

Does the company supply you with ongoing support?
If a company really has developed its own product, or devised a unique system with medical research, then they should provide you with ongoing support to ensure that you are using the system or product appropriately. If a company does not have customer assistance then do not use them.