As far as information about "tapering on" specifically, we're not aware of much in the way of dedicated research or anecdotal data on how to do it. One strategy informed by Alexander Shulgin's approach could be to raise your dose at small, consistent increments (indexed to the dosage range of the particular substance in question) over successive sessions.

For instance, many drug databases like Erowid or PsychonautWiki list a range of dosages from "threshold" to "heavy." You could start at the low end of a "threshold" dose, then do something on the higher end of a threshold dose. Then something on the low end of a "light" dose, then something on the high end of a light dose, and so on.