... the golden rule as someone has mentioned it's a business - so no over decorating , expensive high end fixture/fittings (unless the area demands these) and make sure that you take out references for all your tenants..
We have two properties and we have had our share of "bad tenants" over the years....
My flat in London was let to a chap who paid the first months rent and then stopped paying....it took me 6 months to regain control of the property and when I walked round after he was evicted it was a tip.
He had broken most the internal doors, windows, the bathroom fixtures were hanging off the walls, the carpets were ruined with cigarette burns and the remants of joints everywhere, the walls were disgusting, the kitchen a Rats Fest etc etc etc etc - I guess that this one cost me about 5 grand in lost rent and costs to redecorate - it broke my heart as it was my first flat - I am much much much harder now.
Our other property has also caused some headaches - we had a "lady" with a small baby in there..... the second night she was there she phoned to say that the shed had been broken into and her boyfriend's tools had been stolen therefore she would like a dog (Staffie ??) to protect the house - NO NO NO... Her boyfriend then decides to start a car repair business on the two parking spaces outside - this pissed the neighbours off big time. She paid the rent when she felt like it and had an excuse for everthing - she was astounded that I wanted the property back at the end of her tenancy... She was the tenant from hell.
When I met her to discuss the return of her deposit - I remarked that the full length curtains in lounge were stained with what looked liked baby sick - she said don't be silly - "that's not baby sick it is white chocolate" obviously where he had wiped his hands all down the sides.. She also attempted to redecorate before moving out (in a vain attempt to get her deposit back) - by painting all the walls with gloss paint and leaving the curtains still up, She painted down the sides of curtains,poles and rings, the window frames closed and the doors and carpet .... and the list went on and on and on...
So I guess my view is - no-one will treat your property as their own (unless you are very lucky) - get yourself a good list of local tradespeople that can step in quickly and help with repairs etc, nuture some friendships with neighbours before you let (they can report back on the comings and goings) ,don't fall in love with your rental property, make sure that the figure stack up - and finally choose your tenants with care...