Let's practice:
Exercise 1: http://www.adelescorner.org/grammar/this_that/this_these.html
Exercise2: http://www.adelescorner.org/grammar/this_that/that_those.html
Exercise 3: http://www.adelescorner.org/grammar/this_that/this_etc.html
Exercise 4: http://www.grammar.cl/Games/This_That_These_Those_2.htm
Exercise 5: http://www.grammar.cl/Games/This_That_These_Those.htm
Exercise 6: http://learnenglishkids.britishcouncil.org/en/grammar-games/these-those
Exercise 7: http://www.slideshare.net/genemstcruz/demonstratives-pronouns-game
Exercise 8: http://www.englishexercises.org/makeagame/viewgame.asp?id=4102
Exercise 9: http://www.grammar.cl/Games/This_That_These_Those_2.htm
Exercise 10: http://www.ihbristol.com/free-english-exercises/test/esol-smc-this-that-these-and-those