Russian Grammar Lesson 13: Possessive Pronouns Мой, Твой, Ваш, Наш, Его, Её, Их
The written lesson to go with this video by Fun Russian is located here. Besides going over (and pronouncing) the different personal pronouns in Russian to match nouns in the nominative case by gender and singular and plural nouns, she goes over how to ask "whose?" in Russian. You'll understand then when to use чей, чья, чьё, or чьи when forming a question.
Here is another article on Russian grammar at Russian for Everyone: Asking Whose in Russian? The Possessive Pronouns его, её, их, наш, ваш. This page has some sample sentences with audio files, and some online exercises to complete at the bottom. This page explains the difference between the possessive pronoun Ваш and ваш. In one of the exercises you need to know the difference.