"Give me a plate, please."
Translation:Дайте, будь ласка, тарілку.
The problem here is that not specified who are we talking to. If you are talking to a stranger or an older one, and asking them to do something for you. It is better to ask that in formal way like 'Дайте'. If you ask the same, a peer or a person that younger than you, you can do that in informal way like 'Дай'.