How to start an adaptation
There's several methods for adapting to a new schedule. The by far most common one is cold turkey, which is also the best for jumping into polyphasic sleep from monophasic sleep. Between schedules, it can be a bit more complicated and depends on the individual - but some form of rhythmic preservation may be helpful.Cold Turkey
This is the recommended mode of adaptation for most. You just jump in. Unlike what some old sources may tell you, not sleeping for a day is not beneficial for speed (stage-3), so it makes sense to not skip your core nor naps on the first day of adapting, and just start following your schedule from the moment you decide to start it.Naptation
Naptation, or CL12, is a schedule meant to be used as a transition for first-time polyphasers to learn high quality napping. Like CL6 (Uberman), it is generally not something you can adapt to, but it's not meant for that. Once you feel you've got the hang of napping, you switch cold-turkey to your desired schedule.Gradual adaptation
Gradual adaptation is a process of reducing (or extending) over time, but not by-the-minute, instead by the cycle (for cores) and by number for the naps. This means each step of the way is usually a different schedule wholly. An exception is flexing adaptations, which qualify as gradual adaptation, but do not alter TST or sleep time for any individual phase.Each transitional schedule must be adapted to before switching to the next, if there are multiple. This takes a long time.
Some schedules can only be reached gradually. TST that's on the edge of what you can do may become [more] reachable, and schedules that cannot be adapted to cold turkey (like any -flex schedule and derivatives like MOCAMAYL, and possibly some normally unviable schedules due to long gaps or similar) are made possible.