Under the rules of science, people who make the claims bear the burden of proof. It is their responsibility to conduct suitable studies and report them in sufficient detail to permit evaluation and confirmation by others. Instead of subjecting their work to scientific standards, promoters of questionable "alternatives" would like to change the rules by which they are judged and regulated. "Alternative" promoters may give lip service to these standards. However, they regard personal experience, subjective judgment, and emotional satisfaction as preferable to objectivity and hard evidence. Instead of conducting scientific studies, they use anecdotes and testimonials to promote their practices and political maneuvering to keep regulatory agencies at bay.
What most sets alternative medicine apart is that it has not been scientifically tested and its advocates largely deny the need for such testing. By testing, we mean the marshaling of rigorous evidence of safety and efficacy. Of course, many treatments used in conventional medicine have not been rigorously tested, either, but the scientific community generally acknowledges that this is a failing that needs to be remedied. Many advocates of alternative medicine, in contrast, believe the scientific method is simply not applicable to their remedies.
Alternative medicine also distinguishes itself by an ideology that largely ignores biologic mechanisms, often disparage modern science, and relies on what are purported to be ancient practices and natural remedies (which are seen as somehow being simultaneously more potent and less toxic than conventional medicine). Accordingly, herbs or mixtures of herbs are considered superior to the active compounds isolated in the laboratory.