The hinges and latch assembly on the doors, 
Hood and the trunk should be lubricated with few drops of light oil or lock lubricant every 3000 miles or every three months. Further, one has to ensure that the door latch strikers are covered with a layer of grease to reduce the rate of rust and facilitate smooth functioning. It is also good to spray some lubricant on the door and trunk lock with spray-on graphite lubricant.