How do I choose between “can” and “could”? [duplicate]

Question

1. Where can we go?
2. Where could we go?

1. Can you pass me the salt?
2. Could you pass me the salt?

Which sentence is more appropriate and why? What are the differences?

Answer 1

1. Where can we go?
2. Where could we go?

Both are asking for a suggestion on where to go. I think their meanings are almost the same except that the latter one is a bit more "uncertain" of their destination. And it sounds more like "Let's discuss where we would go."

1. Can you pass me the salt?
2. Could you pass me the salt?

These also mean the same thing, but in this case, the first one is more informal and can be spoken between close people, whereas the second one is more polite and formal.