The inventory
Photograph every room, every appliance and every existing mark on the day you get the keys, and date the file. That is the evidence.
What to photograph
Every room from the doorway, then close-ups of anything already damaged. Meter readings on the same day.
What to write down
Serial numbers of appliances, the state of the floors, and anything the landlord promised to fix.
Why it matters later
A deposit dispute is decided on evidence. The side with dated photographs usually wins.
Read next: deposit rules, notice periods.