With another person you tell a story together. Person one says the first sentence. Person two repeats the first sentence and then adds the second sentence. Person one then repeats sentence one and two and adds a third sentence and so on until you have a story of seven sentences. (why 7? no reason just sounds nice).
The story of seven sentences should be repeated a few times by each person until the errors are minimal. (someone who knows the language well should be monitoring this) It should then be written down either there and then or later at home. This activity worked very well on a one to one basis, is often funny and cements chucks of language into the brain that otherwise would drift off like smoke from a cigarette.