For a destination that appears in so many photographs, I would begin a Santorini plan with a quieter question: what do I want an ordinary day there to feel like? A few practical decisions can make that answer easier to carry into the trip.
Set the pace before booking
Write down the kind of trip you want: long walks, time by the water, cultural visits or mostly rest. Choose one main activity per day and leave room around it. A beautiful hotel photograph tells you little about how convenient or comfortable its setting will be for your needs.
Ask practical accommodation questions
Before paying, confirm access, stairs, luggage assistance, cancellation terms and the facilities that matter to you. Compare the full cost rather than a headline nightly rate. Use current information from the property itself and save its written answers with your reservation.
Keep arrival day simple
Allow for the actual journey from your arrival point to the accommodation. Check transport arrangements directly before travel and have an offline copy of the address. I would avoid making a timed excursion the first obligation after a long journey.
Build a plan you can change
Keep a short list of possibilities instead of an hourly schedule. Weather, transport and energy can change a day. Confirm opening times and any booking requirements close to the visit. Comfortable footwear, suitable sun protection and drinking water deserve room in the bag before another outfit does.
Keep your booking details, transport information and a small list of possibilities together. A clear plan should give the trip room to breathe.