The faq advises being "not full, not hungry". Sound advice. If you are potentiating with harmalas, SWIM recomends trying them first on their own to get a baseline feel - she did this recently and it was pleasant and, surprisingly, kept her awake. Rue tea/extracts can cause mild digestive tract discomfort in some folks. Different DMT extractions cause slightly different "body loads". Best not to be ravenous or stuffed, and best to abide by some dietary restrictions in the meal preceeding the experience. I don't know the whole list of foods which are dicouraged but info here is abundant.
Best.
"The first principle is that you must not fool yourself, and you are the easiest person to fool." Richard P. Feynman