Write numbers, not descriptions, for heat
A reptile sitter cannot follow the word warm, so give temperatures as numbers tied to places. Write the basking or warm-end temperature your reptile needs, the cool-end temperature, and the night-time range if it differs, and beside each one write exactly where it is measured: the probe under the basking platform, the digital thermometer at the cool hide, the display on the thermostat itself. Naming the instrument for every number removes that guesswork. Add what the thermostat should be set to and whether its display shows the set temperature or the measured one, because confusing those two is a classic first-weekend error.
Explain the heating equipment like a labelled diagram
Walk the sitter through your heat sources one by one, in the order they appear on the enclosure. Name each device, what it does, and what controls it: the basking lamp on its timer, the heat mat under its thermostat, any ceramic heater that gives heat without light. State plainly which plug each device lives in, and support the words with a labelled photograph of the full setup, cables and all, taken from where the sitter will stand. Give the light cycle as clock times, and say the enclosure should be fully dark at night so nobody mistakes the plan for a failure.
Write misting as times, duration, and a result to check
Misting instructions fail when they say mist twice a day and stop there. Give the sitter the clock times you mist, roughly how long you mist for, and, most usefully, what should be true afterwards: droplets standing on the leaves and glass, the humidity reading risen into the range you have written down, the substrate surface damp but not flooded. Name the water to use, where it is kept, and how the sprayer fills. If your reptile drinks from droplets rather than a bowl, say so in bold terms, since for those species a skipped misting is a skipped drink, not a cosmetic omission.
Give a short if-this-then-that list for drifting readings
Readings will drift while you are away, and a good instruction sheet tells the sitter what to do before they phone you in a worry. Write the small number of checks in order: if the warm end reads low, confirm the lamp is on and the thermostat probe has not been knocked off its spot; if the enclosure reads hot, check that the room itself is not overheating and that no heat source is running unplugged from its thermostat. State which adjustments the sitter may make, such as reseating a probe, and which they must never make, such as plugging a heat mat straight into the wall to warm things up faster. Then give the readings that mean phone you the same day, and the animal signs, like constant gaping or hiding only at the cool end, that mean phone a vet.
Test the sheet before you travel, not during
The only reliable way to know your instructions work is to watch somebody use them. Before the trip, have your sitter do one full round of checks and misting while you stand back and say nothing, and fix every place where they hesitate, misread, or reach for the wrong control. Their questions during that rehearsal are your sheet's gaps, and they are far cheaper to find in your kitchen than over the phone from another time zone. Leave the final version printed at the enclosure as well as shared digitally, with your number and your vet's number at the top of the first page, because the moment instructions matter most is the moment nobody wants to go looking for them.
KinsLe keeps the tested sheet filed under Care Pass on the profile, beside the photograph, for every future absence.