Probably the most important point. Many good opportunities at science are paid for by those who profit from that science:
Who paid for and conducted the study?
This is a somewhat cynical point, but one that’s worth making. The majority of trials today are funded by manufacturers of the product being tested – be it a drug, vitamin cream or foodstuff. This means they have a vested interest in the results of the trial which can affect what the researchers find and report in all sorts of conscious and unconscious ways. This is not to say that all manufacturer-sponsored trials are unreliable. Many are very good. But it’s worth looking to see who funded the study to sniff out a potential conflict of interest for yourself.