Most security deposit disputes come down to one question: what condition was the unit in before this tenant moved in. Whoever has better records wins that argument, and it's almost always the landlord who does the inspection properly.
Photograph everything, with a timestamp. Every room, every wall, every appliance, every fixture, before the tenant moves anything in. Close-ups of anything already worn or damaged. This takes twenty minutes and saves hours of argument later.
Use a written checklist, not just photos. Walls, floors, ceilings, windows, doors, appliances, plumbing fixtures, smoke detectors. Note condition for each: new, good, fair, or damaged, with specifics.
Do it together with the tenant if you can. Walk through it with them, have them initial or sign the checklist. A tenant who agreed to the documented condition at move-in has a much harder time disputing it at move-out.
Test everything that can break. Every faucet, every outlet, the garbage disposal, the smoke detectors, the door locks. Not just visual condition, whether it actually works.
Store it somewhere you'll actually find it in a year or two. A move-in inspection from a tenant who stays five years is only useful if you can still locate it at move-out. Attach it to the property record, not a folder on a laptop that might not exist by then.