Quote Originally Posted by impulse View Post
So how do you say "where did you go"? in Russian?

куда ты ехал? - where were you going? (talking about a specific direction at a specific time)
куда ты поехал? - (you're not here now) "where have you gone?" or colloquially when you see someone about to go somewhere "where are you going?" or (describing a sequence of past events) "where did you go" or more precisely "where did you set off for"
откуда ты приехал сюда.- (you're here now) where have you/did you come from?
куда ты уехал? - same as куда ты поехал? (the difference is that поехал can mean just starting to move, without necessarily implying a direction, while уехал always implies leaving)
куда ты ездил? - where did you use to go? (talking about habitual movement or to multiple places), also Ramil's example is a good one Я видел, как ты выходил из дома вчера, куда ты ходил? it's like asking "where did you go yesterday" you might have left the house and come back multiple times, visited multiple locations, etc.
you also forgot
куда ты съездил? which is the perfective of ездил, referring to a single trip there and back. For example if you just got back from holiday, your friend might ask "куда ты съездил?" and you might reply "Я съездил на море."