Remember that the word "cuándo" can always be used on its own to simply ask "when?" This is valuable for any beginner, even if you can't form the rest of the sentence, as the context will provide the rest of the information to solicit a response for you. Also, you can ask "¿cuándo es?" (when is it?); again, this is another general question which can help you get the information you're looking for, if you find yourself in a tight spot.
Let's briefly note "cuando" and it's function as a conjunction. As such, it links main and subordinate phrases and joins words or sequences. "Cuando" is a temporal conjunction, and in this way, it expresses the temporal relation of the grammatical elements.
Consider the following examples:
Estaré en la oficina cuando llegues a la casa. (I will be at the office, when you get home.)
Cuando vayas al mercado, me compras unas manzanas, por favor. (When you go to the market, pick some apples up for me, please.)
Aside from its syntactic position, the main way to distinguish the usage is by the graphic accent (i.e. "cuando" = conjunction; "cuándo" = interrogative adverb) and by the accentuation on the first syllable, when it is an interrogative pronoun.