How do I know which verb ending to use?

Verbs in Russian change endings or 'decline' depending on who is speaking or being addressed. There are patterns which have to be learned for how to decline verbs, and although there are slight variations, there are no exceptions to the rules, so once you have got the hang of it you are ready to use them! Each verb in its infinitive/dictionary form declines depending on who is speaking or being addressed, so in 1st person singular (I), 2nd person informal (you), 2nd person plural/formal (you pl.), 3rd person singular (he/she), 1st person plural (we) and 3rd person plural (they). For example: "I am reading a book" - use 1st person singular (I) form for verb reading. "Do you know where we are?" - use 2nd person (you) form for verb know. The endings for verbs simply have to be learned, however are not difficult and once learned apply to all verbs.