This worksheet explains the usage of the the common wh- words what, which, who, when, how, why, whom and where. It has a translation exercise that should help students associate the English wh- words with the ones in their own language.
Since this worksheet has somewhat personal questions ("what do your parents do?", "which do you prefer, chocolate or vanilla?", etc) you could use it as an oral exercise to get your students to ask questions to each other and talk about themselves.