checklists

The main thing is .. WRITE EVERYTHING DOWN .. any detail, number, contact, address or whatever, here are some ideas, one list regarding pets, and one for household issues:

Cat/pet need to know information list ideas - 

Food regime, and required medicines (if any, including method of application)
Vet details - contact number, address, pet insurance details, microchip number
Daily feeding routine, treats and toys
Grooming regime and brushes, litter tray
and/or catflap information
Local knowledge re foxes and neighbouring cats if applicable
Habits  - such as a "liking" for running water taps, or bringing "presents"
Advance warning if hairballs or vomit are a frequent issue (I'm used to lots of messy problems of course)
House rules for the pet - rooms or workspaces not allowed for example (and of course kitchen areas)
Would you like weekly/daily updates and photos of your pet?

And similarly a list re household information:

Ideally, a folder with list of numbers re services and emergencies - council, water, electric, gas, insurance etc. and instruction manuals for kitchen appliances, heating system and suchlike.
Contact information for a friend, neighbour, or relative with spare key in case of emergency - also another local pet-sitter who could be called on at very short notice 
Alarms - fire, security, carbon monoxide
House rules for the house-sitter (no shoes rooms or areas, dietary rules for religious reasons etc.)
Notice re any deliveries expected, cleaner days and times, gardeners, building work, guest who might visit, mail requiring action (this usually involves parking tickets or congestion charge issues)
Wifi code and location of modem
Landline, nuisance call issues, any important calls expected (only ever seem to be NHS related nowadays)
Fuse box, tool box, and WD40!
Heating switches, kitchen appliance operations, bathroom taps and shower problems
Plants outdoor or indoor watering, garden mowing
Rubbish and recycling times and days
Local area specific knowledge for important potential incidents re neighbours (health service visits or likely police visits for example).

BTW, one of my favourite cats "pan" did look exactly like this as a kitten, well except for the wings, but yes with the teeth - hence am borrowing this photo from the interweb ...