When you rent the flat, make a video and click photgraphs of the property you are renting in the presence of the owner of the flat. when you are vacating, the amount can be deducted only for major wear and tear or anything as per the clause in your registered/notarised rent agreement. you can compare the property and see how much damages are reasonable to be claimed by the landlord and thats how you can secure your security deposit with the landlord.