Do the exercises:
http://www.ego4u.com/en/cram-up/tests/hadrians-wall
http://www.helpforenglish.cz/article/2006081101-cviceni-cinny-a-trpny-rod
http://www.helpforenglish.cz/article/2006080901-cviceni-trpny-rod-tvoreni-trpneho-rodu