1) Seek objective, evidence-based confirmation for the safety and efficacy of any dietary supplement, health-related product or treatment.
 
2) The accepted standard is competent and reliable scientific evidence that has been published in a reputable, peer-review scientific journal:

a) Effects are best confirmed by at least two clinical studies (i.e., studies done with people) by independent researchers, ideally those having no association with the product being tested;
  
b) Research using in vitro techniques, which includes studies using isolated cells outside of the environment of the intact organism, or studies using animal models, can be suggestive of what may or may not take place in humans. This research does not, by itself, provide essential support to make claims for effects in people;
  
c) Studies conducted on people with disease states can offer insight into mechanisms relating to that condition, but without specific supporting evidence it cannot be assumed that the same reactions will occur in otherwise healthy well nourished individuals;
  
d) Before publication, studies should have undergone a substantive peer-review and been published in a reputable journal (ideally one indexed by the National Institutes of Health - pubmed.com) with all conflicts of interest being clearly revealed;
  
e) The evidence must be applicable to the substance or product being used as directed for the conditions being promoted, and for the same types of individuals on whom the supporting research was conducted.

3) Testimonials are designed to be seductive and sound convincing! They should not be the sole reason you decide to buy a product.
 
4) Don't be persuaded when the only available source of "positive" information comes from individuals or entitles that benefit from the sale.
  
5) The concept of "they couldn't say that if it wasn't true," is misleading. There are varieties of ways by which dietary supplements and other health products get promoted; regulatory agencies cannot be expected to keep up with the ever-changing frontier of false, illegal and questionable claims being made.
 
6) Be aware that the ingredients in dietary supplements can interact with each other, and with prescription medications. Be up front about what you are taking with any health professionals entrusted with your care.