There are several broad characteristics of pyramid schemes. Scheme collapses if growth ceases. Program of negative value until new rep achieves a lofty bonus level. Claims of specific high income. You can't earn more than your sponsor.
Founders are often invisible.
Often, a pyramid relies heavily or exclusively on the enrollment income, and has no on-going income from other sources. Be particularly careful if they have no same-customer repeat sales. Sometimes you may also be told that you must decide to enroll before leaving the presentation, or else forfeit your opportunity to enroll. Reputable programs teach their people to avoid high pressure techniques, on the principle that anyone who has to be coerced into registering will probably not take the initiative to regularly order products for their own use, much less present the plan to anyone else. Because a pyramid scheme relies on enrollment fees or a worthless product, its lifeblood is new enrollments.